* add unit tests
* add test structure
* add unit tests for Registry
* add LoaderRegistry unit test
* add unit test for makeSingleton
* add type check
* add plugin data structures
* simplify API
* add preset tests
* update test message
* fix lint
* update makeSingleton
* update Plugin, Preset and unit test
* revise Registry code
* update unit test, add remove function
* update test
* update unit test
* update plugin unit test
* add .keys(), .entries() and .entriesAsPromise()
* update test description
