Update PR guidelines

Reviewed By: mkonicek

Differential Revision:D3035945
Ninja: oss docs

fb-gh-sync-id: 5569d266330d5ecb232d16b5100e3f12717acf4c
shipit-source-id: 5569d266330d5ecb232d16b5100e3f12717acf4c

docs/PullRequestGuidelines.md

@@ -1,4 +1,4 @@
-Here are some tips on how you can help review pull requests:
+Here are some tips on reviewing pull requests:
 
-- Does the PR miss info required in the [Pull request template](https://github.com/facebook/react-native/blob/master/PULL_REQUEST_TEMPLATE.md)? Ask for it and link to the template.
-- Does the code style match the [Style guide](https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md#style-guide), especially consistency with the rest of the code? If not, link to the style guide.
+- Does the PR miss info required in the [Pull request template](https://github.com/facebook/react-native/blob/master/PULL_REQUEST_TEMPLATE.md)? Ask for it and link to the template. Add labels 'Needs revision' and 'Needs response from author'. Examples: [#6395](https://github.com/facebook/react-native/pull/6395), [#5637](https://github.com/facebook/react-native/pull/5637).
+- Does the code style match the [Style guide](https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md#style-guide), especially consistency with the rest of the codebase? If not, link to the style guide and add the label 'Needs revision'.