Update contributing

Author: benjie

CONTRIBUTING.md

@@ -2,10 +2,13 @@
 
 This package uses a custom publish flow.
 
+**IMPORTANT**: Do not push directly to `main` - every change must go through a PR
+otherwise changelog generation will fail.
+
 ```sh
 npm install
 npm version patch # or minor or major
-git push && git push --tags
+git push --follow-tags
 npm run build
 cd npmDist
 npm publish --tag=next
@@ -18,3 +21,9 @@ All good? Publish:
 ```sh
 npm dist-tags add graphql-relay@VERSION_NUMBER latest
 ```
+
+Finally generate the CHANGELOG:
+
+```sh
+node resources/gen-changelog.js
+```