Add readme command

[alysbrooks]

Added a command to create a project README like I proposed in Clojurians Slack.

This is a straightforward change in terms of code. The main questions are more about ergonomics and the interface rather than technical or implementation details:

• Should we create a docs subcommand (like it is now) or should readme be a top-level command? add readme was @borkdude's suggestion
• Can we fill in more information automatically?
• Could we prompt for more information? (Maybe a follow up PR?)

README and README templates I checked

• Babashka
• Leiningen new
• Probably some I'm forgetting now

Template

• This PR corresponds to an issue with a clear problem statement : Add a command to create README #157

• I have updated the CHANGELOG.md file with a description of the addressed issue.

[borkdude]

From slack:

I think neil add readme is a reasonable choice to start with. If we need to add more we can group it under neil doc whatever later
8:18 PM
I think a cool feature would be to auto-update the version in a README, as the version is saved in deps.edn :aliases :neil :project :version
8:18 PM
but perhaps that's a bit of a stretch
8:20 PM
but the general idea seems ok to me
8:21 PM
I'd call the command neil add readme for now

[alysbrooks]

I'm not sure about creating a whole version update mechanism in this PR, but maybe I could add a placeholder so people who use the command now can benefit from version updates in the future.

[borkdude]

@alysbrooks Yeah, out of scope for this one I'd say, just a future idea

[alysbrooks]

I created #157 to document the original idea so we don't have to rely on Slack.

[alysbrooks]

I could autogenerate instructions for adding it as a dependency to Leiningen, Boot, and the Clojure CLI, but I'm not sure where the group id should come from

[borkdude]

group id comes from :aliases :neil :project :name and the namespace thereof I think?