docs: improve development workflow linting and testing guidelines

[rohitpaulk]

Update the development workflow documentation to clarify the linting
and testing process. Advise running npm run lint after making
changes and only running tests selectively using npx run ember test
with module names, instead of using slow commands like npm test or
npm run test. Provide guidance on finding the module name in test
files or asking for help when unsure.

[github-actions]

Test Results

  1 files  ±0    1 suites  ±0   8m 55s ⏱️ -34s
665 tests +5  617 ✅ +6  48 💤 ±0  0 ❌ ±0 
665 runs  +5  617 ✅ +7  48 💤 ±0  0 ❌  - 1 

Results for commit 92f18b7. ± Comparison against base commit 83b0d52.

This pull request removes 1 and adds 6 tests. Note that renamed tests count towards both.

Chrome ‑ error

Chrome 140.0 ‑ Acceptance | course-admin | view-submissions: it should be able to filter by stage(s) through a dropdown menu
Chrome 140.0 ‑ Acceptance | course-admin | view-submissions: it should be accessible if user is course author and authored current course
Chrome 140.0 ‑ Acceptance | course-admin | view-submissions: it should handle null value for tree SHA
Chrome 140.0 ‑ Acceptance | course-admin | view-submissions: it should have the commit SHA in the header
Chrome 140.0 ‑ Acceptance | course-admin | view-submissions: it should have the tree SHA in the header
Chrome 140.0 ‑ Acceptance | course-admin | view-submissions: it should not be accessible if user is course author and did not author current course

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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