feat: Add Issue section to PR template (Codecademy#4259)

* feat: Add Issue section to PR template

* fix: revise formatting

* fix: change sentence in the last checkbox

* fix: revise sentences

Co-authored-by: Ishwari Garge <[email protected]>

* Format error

---------

Author: CBID2

.github/PULL_REQUEST_TEMPLATE.md

@@ -19,6 +19,13 @@ Of course, you can opt not to do this and be listed as an "Anonymous contributor
 
 <!-- Please write a summary of the change, such as which topic(s) and file(s) that you have edited or created. Please also include relevant motivation and context: -->
 
+### Issue Solved
+
+<!--
+Please use the following format(s) to link the issue numbers that your contribution addresses:
+Closes #issue-number (where `issue-number` corresponds to the PRs' respective issue)
+-->
+
 ### Type of Change
 
 <!--- Please delete or cross off the bullet point(s) that are irrelevant to this PR: -->
@@ -39,7 +46,7 @@ Of course, you can opt not to do this and be listed as an "Anonymous contributor
 - [ ] I have made corresponding changes to the documentation if needed.
 - [ ] I have confirmed my changes are not being pushed from my forked `main` branch.
 - [ ] I have confirmed that I'm pushing from a new branch named after the changes I'm making.
-- [ ] Under "Development" on the right, I have linked any issues that are relevant to this PR (write "Closes #<issue number> in the "Description" above).
+- [ ] I have linked any issues that are relevant to this PR in the `Issues Solved` section.
 
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