Filter CI on PR contents + Mergify support

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,3 +1,19 @@
+<!--
+First, please ensure that the title of your PR is sufficient to include in the next changelog.
+Refer to https://github.com/ucb-bar/chipyard/releases for examples and feel free to ask reviewers for help.
+
+Then, make sure to label your PR with one of the changelog:<section> labels to indicate which section
+of the changelog should contain this PR's title:
+  changelog:added
+  changelog:changed
+  changelog:fixed
+  changelog:removed
+
+If you feel that this PR should not be included in the changelog, you must still label it with
+changelog:omit
+
+Provide a brief description of the PR immediately below this comment, if the title is insufficient -->
+
 **Related PRs / Issues**:
 <!-- List any related PRs/issues here, if applicable -->
 
@@ -17,11 +33,11 @@
 <!-- must be filled out completely to be considered for merging -->
 **Contributor Checklist**:
 - [ ] Did you set `main` as the base branch?
+- [ ] Is this PR's title suitable for inclusion in the changelog and have you added a `changelog:<topic>` label?
+- [ ] Did you state the type-of-change/impact?
 - [ ] Did you delete any extraneous prints/debugging code?
+- [ ] Did you mark the PR with a `changelog:` label?
 - [ ] (If applicable) Did you add documentation for the feature?
 - [ ] (If applicable) Did you add a test demonstrating the PR?
-<!-- Do this if this PR is a bug fix that should be applied to master -->
-- [ ] (If applicable) Did you mark the PR as "Please Backport"?
-
-**Release Notes**
-<!-- Text from here to the end of the body will be considered for inclusion in the release notes for the version containing this pull request. -->
+<!-- Do this if this PR is a bugfix that should be applied to the latest release -->
+- [ ] (If applicable) Did you mark the PR as `Please Backport`?