Add support for `deps-new`

Overview

I'm working on a PR for neil (https://github.com/babashka/neil/pull/51) which will make it possible to simplify the "Quick start" for Kit:

brew install clojure babashka/brew/neil
neil new io.github.kit-clj/kit yourname/app

Requirements

• Add a deps-new template to the kit repo
  • Docs: https://github.com/seancorfield/deps-new
  • Example: https://github.com/kit-clj/kit/compare/25b784c9a8e885bedb964dd067761545f6ce23b1...rads:kit:master
• Update the README with the new "Quick start" instructions listed above

Performance

The neil new command is using babashka to run org.corfield.new/create which removes the JVM startup time. I haven't ported the lein-template to deps-new so I can't do a direct comparison yet. That said, with the built-in app template, the difference is significant (3s down to 0.1s):

$ time clojure -Tnew app :name yourname/app :force true
Generating a project called app based on the 'app' template.
clojure -Tnew app :name yourname/app :force true  3.04s user 0.13s system 205% cpu 1.542 total

$ time ./neil new app yourname/app --overwrite
Creating project from org.corfield.new/app in app
./neil new app yourname/app --overwrite  0.10s user 0.03s system 88% cpu 0.147 total

Read the deps-new documentation and the linked kit comparison first, then inspect the existing project template structure and README. Add the kit deps-new template so neil new io.github.kit-clj/kit yourname/app works, and update the README Quick start instructions; done means both the generated project and documented command are usable.