Add unit tests and improve page identification logic

[thelearned1]

What

This PR makes several improvements to testing, testability, and to the logic around which Wikia/Fandom pages correspond to which UESP pages.

Why

The overarching goal is to improve UX and to generally increase the utility of what is already an awesome extension.

That said, I do recognize that this PR is somewhat out of the blue. It seemed to me that there is already some logic in the present version of the extension that attempts to correctly identify the UESP namespace of a given ESWiki page based on its title. However, because the default strategy is to search UESP for whatever title is identified, the current iteration has some drawbacks for pages of certain types. My additions try to reduce some of those drawbacks.

As evidenced by the provided tests, this has been somewhat successful (though admittedly I wrote them :-P). Coverage at identifying the exact correct UESP name, or name that redirects to correct UESP page, increases from 27 to 96 of 274 pages (9.8% to 35%). See the "Testing" section for a thorough breakdown and description of my testing approach.

How

• Separate out the logic for generating a page name into a function (for testability, maintainability, and elegance).
• Create build script for recombining function and module into background script (as Firefox does not currently support loading background scripts as ES6 modules in extensions)
• Add Jest unit tests for the aforementioned function
• Add additional heuristics for determining which UESP page should result from a given ESWiki url in function:
  • If an ESWiki page is in the "Portal" namespace and contains the name of a game X, redirect to the UESP page X:X (e.g. "Portal:Skyrim" redirects to "Skyrim:Skyrim")
  • If the user navigates to a Skyrim Wiki page, send them to the corresponding page in the "Skyrim" UESP namespace (e.g. https://skyrim.fandom.com/wiki/Guild_Master's_Gloves searches UESP for the page "Skyrim:Guild Master's Gloves")
  • If the user navigates to the home page of the Skyrim wiki, they are redirected to the Skyrim homepage on UESP (Skyrim:Skyrim)
  • If the user navigates to the home page of the Elder Scrolls wiki, they are redirected to the main page of the UESP (https://en.uesp.net/wiki/Main_Page)

Testing

I add tests only for the function that maps ES Wiki pages to UESP pages, since the rest of the extension remains unchanged.

There are three categories of tests from four data sources:

1. Tests of ES Wiki page names from a set of 200 random ES Wiki pages (collected via the Mediawiki API)
2. Tests of Skyrim Wiki page names from a set of 50 random Skyrim Wiki pages (collected via the Mediawiki API)
3. Tests of "special" pages on either wiki:
   1. All pages on the ES wiki in the "Portal" namespace
   2. A set of 9 possible URLs for the home page of the ES and Skyrim wikis

Tests were run with Jest, and are located in the __tests__ directory.

Results

Results for the original extension were as follows:

__tests__/randomPage.test.js
  random elderscrolls.fandom.com pages: 
     PASS:  27
     FAIL: 173
    TOTAL: 200

__tests__/skyrimWiki.test.js
  random skyrim.fandom.com pages: 
     PASS:   0
     FAIL:  50
    TOTAL:  50

__tests__/homepage.test.js
  elderscrolls.fandom.com portal pages:
     PASS:   0
     FAIL:  15
    TOTAL:  15
  URLs that point to the main page of either wiki:
     PASS:   0
     FAIL:   9
    TOTAL:   9

Test Suites: 3 failed, 3 total
Tests:       247 failed, 27 passed, 274 total
Snapshots:   0 total
Time:        0.89 s
Ran all test suites.

Results for the variation in this PR:

__tests__/randomPage.test.js
  random elderscrolls.fandom.com pages: 
     PASS:  27
     FAIL: 173
    TOTAL: 200

__tests__/skyrimWiki.test.js
  random skyrim.fandom.com pages: 
     PASS:  47
     FAIL:   3
    TOTAL:  50

__tests__/homepage.test.js
  elderscrolls.fandom.com portal pages:
     PASS:  14
     FAIL:   1
    TOTAL:  15
  URLs that point to the main page of either wiki:
     PASS:   8
     FAIL:   1
    TOTAL:   9

Test Suites: 3 failed, 3 total
Tests:       178 failed, 96 passed, 274 total
Snapshots:   0 total
Time:        0.971 s, estimated 1 s
Ran all test suites.

I aggregated these data for the purpose of this PR; the raw outputs of the test suite can be found in the attachments under "testResults-old.txt" and "testResults-revised.txt", respectively.

Supplemental Note: Testing Methodology

I should start by noting that my baseline assumption was that the extension is correct only when it has successfully redirected an ESWiki page to the most closest-corresponding UESP page. Thus, I considered a case where the correct UESP page appeared in the search results a failure for the purpose of unit testing, despite this having only a slight negative impact on UX. That said, I constructed my tests such that a test case would pass if any of the following was true:

1. There is a single UESP page corresponding to the ES Wiki page, and the UESP wiki is searched for the title of that page exactly (and thus sent to the page). Example: "Hammerfell (Arena)" is redirected to "Arena:Hammerfell", and "Yashurah" is redirected to "Online:Yashura".
2. There are multiple UESP pages corresponding to a single ES Wiki page, and the UESP wiki is a searched for a search term which includes all such pages in the search results. Example: "The Vagaries of Magicka" results in searching for "The Vagaries of Magicka" (the ESWiki page includes information about this book in both Morrowind and Battlespire)
3. There is no UESP page corresponding to the ES Wiki page, but the relevant information is contained within a different page, and the extension redirects to this page. Example: "Steel Claymore (Arena)" redirects to "Arena:Claymores", and "Characters (Dragonborn)" redirects to "Skyrim:People"
4. There is no UESP page corresponding to the ES Wiki page and the relevant information is not found anywhere on the UESP wiki; the extension does not redirect anything. Example: Copperhouse Manor (a Daggerfall dungeon) does not have a UESP page and is not included on any of the UESP lists of Daggerfall dungeons.

testResults-revised.txt
testSummary-old.txt

[thelearned1]

The README will also need to be updated to reflect changes in how the extension is built, but I will wait until I have a response on this PR first. Sorry — totally spaced on that!