chore: Update GitHub pull-request template to the latest from `y-scop…

…e/public-repo-template`. (#704)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,16 +1,37 @@
+<!-- markdownlint-disable MD012 -->
+
 <!--
 Set the PR title to a meaningful commit message that:
-- follows the Conventional Commits specification (https://www.conventionalcommits.org).
-- is in imperative form.
+
+* is in imperative form.
+* follows the Conventional Commits specification (https://www.conventionalcommits.org).
+  * See https://github.com/commitizen/conventional-commit-types/blob/master/index.json for possible
+    types.
+
 Example:
+
 fix: Don't add implicit wildcards ('*') at the beginning and the end of a query (fixes #390).
 -->
 
 # Description
+
 <!-- Describe what this request will change/fix and provide any details necessary for reviewers. -->
 
 
 
+# Checklist
+
+<!-- Ensure each item below is satisfied and indicate so by inserting an `x` within each `[ ]`. -->
+
+* [ ] The PR satisfies the [contribution guidelines][yscope-contrib-guidelines].
+* [ ] This is a breaking change and that has been indicated in the PR title, OR this isn't a
+  breaking change.
+* [ ] Necessary docs have been updated, OR no docs need to be updated.
+
 # Validation performed
+
 <!-- Describe what tests and validation you performed on the change. -->
 
+
+
+[yscope-contrib-guidelines]: https://docs.yscope.com/dev-guide/contrib-guides-overview.html