Update CONTRIBUTING.md with some advice about install_local.py

[kenxu95]

Describe your changes and why you are making these changes

I was just going over the CONTRIBUTING.md since I'd like to link that to our contributor. It looks good but I wonder if we can help them save some time by not having to rebuild the UI each time if they don't have to?

Related issue number (if any)

Loom demo (if any)

Checklist before requesting a review

• I have created a descriptive PR title. The PR title should complete the sentence "This PR...".
• I have performed a self-review of my code.
• I have included a small demo of the changes. For the UI, this would be a screenshot or a Loom video.
• If this is a new feature, I have added unit tests and integration tests.
• I have run the integration tests locally and they are passing.
• I have run the linter script locally (See python3 scripts/run_linters.py -h for usage).
• All features on the UI continue to work correctly.
• Added one of the following CI labels:
  • run_integration_test: Runs integration tests
  • skip_integration_test: Skips integration tests (Should be used when changes are ONLY documentation/UI)

[likawind]

Thanks!! This will be very helpful!