W-22970552: Skip PR CI for doc-only changes

[wmathurin]

Summary

Add paths-ignore to the PR workflow trigger so that pull requests touching only documentation files (.md, LICENSE, .gitignore, CODEOWNERS) skip CI entirely.

Change

paths-ignore:
  - '**/*.md'
  - 'LICENSE'
  - '.gitignore'
  - 'CODEOWNERS'

Why

Running full build and test suites on doc-only PRs wastes CI resources with no benefit — documentation changes cannot affect build or test outcomes. Nightly workflows are intentionally unchanged.

GUS

W-22970552

Test plan

• Open a PR touching only a .md file — CI should not trigger
• Open a PR touching a source file + a .md file — CI should trigger normally

[github-actions]

	Tests	Passed ✅	Skipped	Failed
iOS ^18 Test Results	35 ran	35 ✅

Test	Result
No test annotations available

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
iOS ^26 Test Results	35 ran	34 ✅		1 ❌

Test	Result
iOS ^26 Test Results
ReactMobileSyncTests.testCleanResyncGhosts()	❌ failure