RFC: Add advanced typing to your hal json vuex

[manuelmeister]

I tried to create a generic typing system that allows one to define the types to be used further.

In tests/testtypes.ts you can see the definition of the whole endpoint and below it's usage and type autocompletion/errors.

What do you think about the ability to further type methods of hal-json-vuex.

(Currently the _storeData is not exactly perfectly typed. But usually you don't use these as a library consumer)