Clarify pull request template

Author: mpilgrem

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,8 +1,8 @@
-Note: Documentation fixes for https://docs.haskellstack.org/en/stable/ should target the "stable" branch, not master.
+Note: Fixes for the online documentation of the current Stack release (https://docs.haskellstack.org/en/stable/) should target the 'stable' branch, not the 'master' branch.
 
-Please include the following checklist in your PR:
+Please include the following checklist in your pull request:
 
-* [ ] Any changes that could be relevant to users have been recorded in the ChangeLog.md
-* [ ] The documentation has been updated, if necessary.
+* [ ] Any changes that could be relevant to users have been recorded in ChangeLog.md.
+* [ ] The documentation has been updated, if necessary
 
 Please also shortly describe how you tested your change. Bonus points for added tests!