docs: add GitHub release changelog configuration (#229)

This PR adds a GitHub release configuration, which should simplify
changelog generation.

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,10 @@
+Fixes #
+
+### What Changed?
+<!-- Describe the changes made in this pull request -->
+
+### Reviewer Checklist
+
+- [ ] New features are tested and documented
+- [ ] PR has one of the `changelog-X` labels (if applies)
+- [ ] Code deprecates any old functionality before removing it

.github/release.yml

@@ -0,0 +1,33 @@
+changelog:
+  exclude:
+    labels:
+      - ignore-for-release
+  categories:
+    # vulnerabilities
+    - title: Security 🔒
+      labels:
+        - changelog-security
+    # new features
+    - title: Added 🎉
+      labels:
+        - changelog-added
+    # changes in existing functionality
+    - title: Changed 🛠
+      labels:
+        - changelog-changed
+    # soon-to-be removed features
+    - title: Deprecated ⚠️
+      labels:
+        - changelog-deprecated
+    # now removed features
+    - title: Removed 🗑
+      labels:
+        - changelog-removed
+    # documentation was added or changed
+    - title: Documentation 📚
+      labels:
+        - changelog-documentation
+
+    - title: Other Changes
+      labels:
+        - "*"