Update PULL_REQUEST_TEMPLATE.md

Author: Kyaa-dost

.github/PULL_REQUEST_TEMPLATE.md

@@ -38,6 +38,7 @@ Please check if your PR fulfills the following requirements:
 - [ ] Pull Request has been submitted to the documentation repository [instructions](..\contributing.md#docs). Link: <!-- docs PR link -->
 - [ ] Sample in sample app has been added / updated (for bug fixes / features)
     - [ ] Icon has been created (if new sample) following the [Thumbnail Style Guide and templates](https://github.com/windows-toolkit/WindowsCommunityToolkit-design-assets)
+- [ ] New major feature/change in the toolkit and documents have or will be added to the [Wiki](https://github.com/windows-toolkit/WindowsCommunityToolkit/wiki)
 - [ ] Tests for the changes have been added (for bug fixes / features) (if applicable)
 - [ ] Header has been added to all new source files (run *build/UpdateHeaders.bat*)
 - [ ] Contains **NO** breaking changes