[infra] auto-publish pre-releases (#2190)

Author: dcharkes

.github/workflows/publish.yaml

@@ -9,6 +9,7 @@ on:
     # TODO: Enable autopublishing for these when Flutter SDK is supported.
     tags:
       - '[A-z0-9]+-v[0-9]+.[0-9]+.[0-9]+'
+      - '[A-z0-9]+-v[0-9]+.[0-9]+.[0-9]+-[A-z0-9]+'
       - '!ffigen-v**'
       - '!jni-v**'
       - '!jnigen-v**'