Commit lein-generated `core/pom.xml` for clojure programs to use as a git lib

[kjothen]

• Related to issue #161, this stop-gap will allow clojure programs to import Jarl from github, in lieu of a maven repository, as follows:

  {:deps 
  {boregby.jarl 
  {:git/url "https://github.com/borgeby/jarl.git" 
  :deps/root "core" 
  :sha "{{replace with commit hash}}"}}}

• Removed corresponding line from core/.gitignore to exclude pom.xml
• Unrelated to the above, added lines to .gitignore to exclude .lsp\ and .clj-kondo\ directories which get created when developing under emacs with lsp and clc-kondo respectively