Consider adding a README boilerplate for Typelevel projects

[DavidGregory084]

There are certain elements that are generally present on all Typelevel READMEs, things like

• Code of Conduct
• Discord link - maybe just as a badge?
• CI badges

Perhaps we could standardise those things a bit in typelevel.g8?

[rossabaker]

CI badges sound great. Maven Central, too, but I don't know what those do before first release. Markdown or HTML comments would be an option. That won't work for Discord, because most projects won't have a channel at creation (editorial: good!), and the channel URI is not predictable.