build: Updated .vscodeignore (#140)

Updated .vscodeignore to use "whitelist" conventions instead of
"blacklist"

.vscodeignore

@@ -1,19 +1,21 @@
-_ignore/**
-.github/**
-.vscode/**
-.vscode-test/**
-src/**
-packages/**
-.gitignore
-.yarnrc
-vsc-extension-quickstart.md
-**/tsconfig.json
-**/tsconfig.unit.json
-**/tsconfig.tsbuildinfo
-**/.eslintrc.json
-**/*.map
-**/*.ts
-**/__mocks__/**
-e2e/**
-test-reports/**
-icons/**
+### Ignore everything ####
+**/*
+
+#### Explicitly add things back ####
+
+!LICENSE
+!package.json
+!README.md
+
+!assets/**/*
+!docs/**/*
+!images/**/*
+!out/**/*.js
+!snippets.code-snippets
+
+!node_modules/**/LICENSE
+!node_modules/**/package.json
+!node_modules/**/README.md
+
+!node_modules/@deephaven/require-jsapi/**/*.js
+!node_modules/ws/**/*.{js,mjs}

CONTRIBUTING.md

@@ -85,7 +85,8 @@ https://code.visualstudio.com/api/working-with-extensions/publishing-extension#p
 1. Set `VSCE_PAT` env variable to personal access token for a user in the https://dev.azure.com/deephaven-oss/ org.
 1. Increment the version number in `package.json` (be sure to run `npm i` to update package-lock as well)
    > See [versioning strategy](#versioning-strategy) for details on our version number scheme.
-1. Package latest `npm run package:latest` (inspect output for any unexpected files included)
+1. If new content has been added that needs to be packaged that is not included by `.vscodeignore`, make appropriate changes (this should not be common).
+1. Package latest `npm run package:latest` (inspect output to verify included files are as expected)
 1. Use `vsce` cli to publish to Visual Studio Marketplace
 
    ```sh