Allow to provide custom store management engines.

[diegocr]

Currently, the only provided stores are memory and leveldb which are not extensible, and developing new ones requires those to be published under this repository maintenance.

https://github.com/kucherenko/jscpd/blob/1fc50995d26534b84df226ad58c40e7c37d6ec71/packages/jscpd/src/init/store.ts#L7

I would like to suggest the ability to provide a custom-made store engine, similar to the way eslint-plugin-local-rules does work.

i.e. my idea is that through the --store command line option (and/or config file) we can provide a path to a JS file to be loaded and used as store, overriding the default MemoryStore.

Thoughts?

Would you accept a PR implementing such feature?