Automatically label issues based on regular expression matches in title and description

[wknapik]

This is an implementation based on https://github.com/github/issue-labeler. The action has some quirks, but it's maintained by GitHub and security approved. If we don't like the behavior, we could potentially switch to something else, or even implement our own from scratch.

I added some patterns to start, but the expectation is that others would add more.

Please assign as reviewers and/or tag anyone who should see this and comment.

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A
  • https://github.com/brave/brave-browser/wiki/Brave-Wallet

Test Plan:

[kjozwiak]

@wknapik just curious, do we have any example of how the new labels will look with the above change? Once merged, it will scan the body of issues and apply labels automatically? What happens if someone manually adds one of the OS/ labels that we already have created? Will it add another one or just skip it?

[wknapik]

@kjozwiak once merged, each time an issue is opened, or edited, this action would run and add any missing labels based on patterns matched. Each label can only occur once, so there would be no duplication.

[kjozwiak]

@kjozwiak once merged, each time an issue is opened, or edited, this action would run and add any missing labels based on patterns matched. Each label can only occur once, so there would be no duplication.

SGTM 👍 Always ++ on anything that will make life easier. Can always adjust/play it by ear if we notice certain labels not being added or incorrectly being added.

[rebron]

++ LGTM