small edits

.github/PR_TEMPLATE/PULL_REQUEST_TEMPLATE.md

 ### Proposed change(s)
 
-Describe the changes made in this PR. If this is a bug fix or a new feature please provide a link
- to it. 
+Describe the changes made in this PR.
-- [ ] Bug Fix 
-- [ ] New feature 
+- [ ] Bug Fix
+- [ ] New feature
-- [ ] Documentation Update 
+- [ ] Documentation Update
-
-- [ ] Do you have a JIRA ticket that can be attached to this PR?
+- [ ] Do you have useful links such as Github issues, JIRA tickets, ML-Agents forum threads which
+ can be attached to this PR?
-- [ ] I have added updated the changelog (if applicable) 
+- [ ] I have added updated the changelog (if applicable)
 - [ ] I have added necessary documentation (if applicable)
 - [ ] I have updated the migration guide (if applicable)