updating the PR template to incorporate both haddock3 user manual and changelog in the checklist

Author: VGPReys

.github/pull_request_template.md

@@ -4,6 +4,8 @@
 
 - [ ] Tests added for the new code
 - [ ] Documentation added for the code changes
+- [ ] Modifications / enhancements are reflected on the [haddock3 user-manual](https://github.com/haddocking/haddock3-user-manual)
+- [ ] [CHANGELOG.md](CHANGELOG.md) is updated to incorporate new changes
 - [ ] Does not break licensing
 - [ ] Does not add any dependencies, if it does please add a thorough explanation
 
@@ -12,6 +14,7 @@
 
 ## Related Issue
 <!-- If this PR is related to an issue, please link it here -->
+<!-- If this PR is has implication on the haddock3 user manual, please link the PR here -->
 
 ## Additional Info
 <!-- Any additional information that might be helpful, if applicable -->