FIX ref getSourceType for paths with */index.html

[goldhand]

Issue: #10324

• Issue is described in detail at TypeError: "o is undefined" (Storybook 6 and Angular 9.1) #10324 (comment) - in short, if path ends with index.html, storybook breaks. I (along with anyone doing this at my company) can't fix this by removing index.html from the browser url because an internal platform requires it in order to render the file.

What I did

• Changes getSourceType to return 'local' if source matches location with index.html in pathname.
• Added refs.test.js to test this edge case and other cases - I needed to mock different values with the global.location. Not too happy with the implementation but I don't know another way to change a mock module between tests.

How to test

• Unit tests included in PR
• Reproduce:
  • Follow CONTRIBUTING.md steps and run yarn serve-storybooks
  • Navigate to: http://127.0.0.1:8001/official-storybook/index.html
  • See the loading icon does not disappear, "No preview" message visible and no stories listed in nav. Open console for error message.
• Fix:
  • Same steps as above, open http://127.0.0.1:8001/official-storybook/index.html
  • No errors, storybook rendered as expected.

[goldhand]

I'm not sure what the @netlify build check failures are about but trying to debug. I build locally just fine so I'm thinking its some CI task I haven't done...

[goldhand]

Sorry, I should have checked the status of this first but I missed that you already approved this @ndelangen . I did a minor refactor of the test while I was trying to figure out why the netlify checks were failing.

[ndelangen]

I'm on it