chore(*): update PR template with links to related wiki pages

Author: Lipata

.github/PULL_REQUEST_TEMPLATE.md

@@ -9,12 +9,12 @@ Closes #
 
 ### Checklist:
  - [ ] All relevant tags have been applied to this PR
- - [ ] This PR includes unit tests covering all the new code
- - [ ] This PR includes API docs for newly added methods/properties
+ - [ ] This PR includes unit tests covering all the new code ([test guidelines](https://github.com/IgniteUI/igniteui-angular/wiki/Test-implementation-guidelines-for-Ignite-UI-for-Angular))
+ - [ ] This PR includes API docs for newly added methods/properties ([api docs guidelines](https://github.com/IgniteUI/igniteui-angular/wiki/Documentation-Guidelines))
  - [ ] This PR includes `feature/README.MD` updates for the feature docs
  - [ ] This PR includes general feature table updates in the root `README.MD`
  - [ ] This PR includes `CHANGELOG.MD` updates for newly added functionality
  - [ ] This PR contains breaking changes
- - [ ] This PR includes `ng update` migrations for the breaking changes
+ - [ ] This PR includes `ng update` migrations for the breaking changes ([migrations guidelines](https://github.com/IgniteUI/igniteui-angular/wiki/Update-Migrations))
  - [ ] This PR includes behavioral changes and the feature specification has been updated with them