docs: package-name needs to be quoted if scoped

[coreyfarrell]

The README.md example release-please.yml sets package-name: release-please-action. This is good for unscoped packages but for package-name: "@myorg/package" it is mandatory to quote the scoped package name. This tripped me up the first time I attempted to use this package. Partly because I'm not super familiar with yaml parse rules so creating yaml files is often copy-pasta for me.

I'm not sure if you want to just quote the release-please-action in your example or add a comment? I can post a PR if you let me know how you want this handled.

[bcoe]

@coreyfarrell perhaps we could add a note that both mentions that package-name is optional for some types of releasers, e.g., node which reads it from package.json, and that you my want to use a quoted string if you have special characters.