docs: improve addLocatorHandler docs

[dgozman]

No description provided.

[github-actions]

Test results for "tests 1"

1 failed
❌ [installation tests] › playwright-component-testing.spec.ts:21:5 › pnpm: @playwright/experimental-ct-react should work

7 flaky

⚠️ [chromium] › library/tracing.spec.ts:243:5 › should not include trace resources from the previous chunks
⚠️ [chromium] › page/interception.spec.ts:104:3 › should intercept network activity from worker
⚠️ [chromium] › library/tracing.spec.ts:243:5 › should not include trace resources from the previous chunks
⚠️ [chromium] › library/tracing.spec.ts:243:5 › should not include trace resources from the previous chunks
⚠️ [playwright-test] › ui-mode-test-screencast.spec.ts:21:5 › should show screenshots
⚠️ [webkit] › library/browsercontext-reuse.spec.ts:50:1 › should reset serviceworker
⚠️ [webkit] › library/tracing.spec.ts:243:5 › should not include trace resources from the previous chunks

26646 passed, 614 skipped
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Merge workflow run.