Convert project to deps.clj, shadow-cljs

[sritchie]

This PR:

• Converts the project from leiningen to deps.clj
• adds badges to the README with all the new good stuff
• adds a GitHub Action that will release to Clojars when a new "release" on GitHub is created (provided @henrygarner that you add CLOJARS_USERNAME and CLOJARS_PASSWORD secrets to the repository)
• Converts the tests from lein-cljsbuild to shadow-cljs
• adds a DEVELOPING.md with this information
• adds bb.edn with the following tasks available:

test:clj  Run CLJ tests.
test:cljs Run CLJS tests.
release   Release the library to Clojars.
lint-deps Lint dependencies.
lint      Lint source-containing directories with clj-kondo.

New README badges: