docs(CONTRIBUTING): auto tag for gh release, point to repo for changelog

previously the doc was pointing at the published docs site but we can't use
that since the docs site does not actually publish, pending resolution of #559

CONTRIBUTING.md

@@ -90,6 +90,7 @@ Maintainers with write access to the repo and the npm organization can publish n
 1. Push the release notes / version / tag to the repo: `git push --tags`
 1. Create a release on the repo:
     ```
-    gh release create @notifee/react-native@x.y.z --title "@notifee/react-native@x.y.z" --notes "[Release Notes](https://notifee.app/react-native/docs/release-notes)"
+    export TAGNAME=`git tag --list|sort -r|head -1`
+    gh release create ${TAGNAME} --title "${TAGNAME}" --notes "[Release Notes](https://github.com/invertase/notifee/blob/main/docs-react-native/react-native/docs/release-notes.md)"
     ```
 1. Publish to npm: `npm publish`