Deprecate and remove support for badges defined in READMEs

[bmish]

For configs without an emoji specified nor a default emoji (e.g. ✅ for recommended), we currently assume the user will define a badge in their README. I'm not a big fan of badges defined like this. They are brittle and require the user to add custom markdown in the README which can be confusing, and they are only available in READMEs currently, not rule docs (not portable).

Instead, we should suggest users to supply the badge/image markdown using the configEmoji option so that we can automatically use it in any file that the config is mentioned.