chore: cleanup library structure

chore: turn into ES module

  * This is the future, embrace it
  * Simplifies building and testing (mid-term) the library

chore: drop `peerDependencies`

  This should only be used under rare circumstances, where
  "there can only be one" principle must be followed, or the outside
  mandates the dependency to use.

  To consider in the future if this library should even depend on
  dmn-moddle, or just consume a moddle tree.

chore: adjust scripts to conform with standard pattern

  The scripts `all`, `build`, `test` scripts work as expected