Define custom categories for the auto-generated release notes

Define custom categories matching the existing release note sections
so that the auto-generated release notes more closely match the
desired format.

Any items appearing in the 'Other changes to review' category should
be reviewed to determine if they should be included, and if so should
be manually moved to the appropriate category.

Unfortunately it's not possible to include custom header / footer content,
e.g. our attestation or thanks sections, in the auto-generated release
notes so we can't use this approach to produce the complete document.
However, there is an API we can call to generate these release
notes and use the returned content as part of another automation. This
will be based on the `release-draft` Pipeline from the plumbing repo
and delivered in a separate change.

In the meantime, this change still reduces the amount of manual effort
required to create a new release.

.github/release.yml

@@ -0,0 +1,17 @@
+changelog:
+  categories:
+    - title: ✨ Features
+      labels:
+        - kind/feature
+    - title: 🐛 Fixes
+      labels:
+        - kind/bug
+    - title: 🔨 Misc
+      labels:
+        - kind/misc
+    - title: 📖 Docs
+      labels:
+        - kind/documentation
+    - title: Other changes to review
+      labels:
+        - "*"