Unit tests

[OmkarPh]

Also fixes #601

[AyanSinhaMahapatra]

LGTM @OmkarPh, thanks!

Some minor things to note:

1. Are https://github.com/nexB/scancode-workbench/tree/feature/unittests/test-old and https://github.com/nexB/scancode-workbench/tree/feature/unittests/test-db used currently and if not should they not be removed entirely?
2. The husky pre-commit increases the time to create commits, and usually we run only linters and other smaller/faster checks in pre-commits, and not the full test-suite? This time will increase when there are more comprehensive tests so this is something that should be considered.

But we can do these separately too, feel free to merge.

[AyanSinhaMahapatra]

Merging! #591 (review) can be addressed at #556

[OmkarPh]

LGTM @OmkarPh, thanks!

Some minor things to note:

1. Are https://github.com/nexB/scancode-workbench/tree/feature/unittests/test-old and https://github.com/nexB/scancode-workbench/tree/feature/unittests/test-db used currently and if not should they not be removed entirely?

This, was fixed in other branch.
If you see the v4.0-react-typescript branch, these don't exist there

2. The husky pre-commit increases the time to create commits, and usually we run only linters and other smaller/faster checks in pre-commits, and not the full test-suite? This time will increase when there are more comprehensive tests so this is something that should be considered.

But we can do these separately too, feel free to merge.

Ohk, lets discuss about this later