Support release nightlies (#63)

* Support release nightlies

See #62

* Replace == nightly with endsWith nightly

* Use majorMinorMatch, not full match

* Replace more (in-)equality checks

* Reduce number of duplicate CI builds

* Add example to docs

* Tidy up nightly conditions

.github/workflows/example-builds.yml

@@ -1,6 +1,9 @@
 name: Example builds
 
-on: [push, pull_request]
+on:
+  push:
+    branches: ['main', 'master', 'releases/*']
+  pull_request:
 
 jobs:
   test: