Set up PR template and gh-ph

Author: Frederick888

.github/PULL_REQUEST_TEMPLATE.md

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+# Description
+
+# Changes
+<!-- === GH HISTORY FORMAT FENCE === --> <!--
+### [`%h`]({{.url}}/commits/%H) %s%n%n%b%n
+--> <!-- === GH HISTORY FORMAT FENCE === -->
+<!-- === GH HISTORY FENCE === -->
+<!-- Do NOT write here! -->
+<!-- It will be filled in by GitHub Actions automatically. -->
+<!-- === GH HISTORY FENCE === -->
+
+# Checklist
+
+- [ ] I have rebased my branch so that it has no conflicts
+- [ ] I have added tests where appropriate
+
+# Is this a breaking change?
+
+<!-- Yes / No. Reason. -->

.github/workflows/gh-ph.yml

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+name: Pull request history
+
+on:
+  pull_request:
+
+jobs:
+  gh-ph:
+    name: Add commit history to pull request description
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - uses: Frederick888/gh-ph@v1
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}