[FEAT] Support multiple tsconfigs

[teoxoy]

closes #21

Adds support for multiple tsconfigs.
This enables aliasing via compilerOptions.paths for monorepos with multiple tsconfigs
Should also improve performance because the mappers are cached.

Includes a new test and updated docs.
I have also tested the new changes in my own typescript monorepo and everything works as expected.

[teoxoy]

closes #18 too the options obj now defaults to {}
Reference:

https://github.com/alexgorbatchev/eslint-import-resolver-typescript/blob/ad337809a5c287f795e328cbc7a1eeefdfbe0ad9/index.js#L20

[teoxoy]

@bradzacher Can you take a look at this PR? It implements the same functionality as typescript-eslint/typescript-eslint#806
Thanks! :)

[fernandopasik]

Would it be possible to review this @alexgorbatchev or @bradzacher?

[JounQin]

Hi @teoxoy , it seems @alexgorbatchev has 'disappeared' for a few months, or he just forgot this project, so I'm going to fork this repository and republish it as eslint-import-resolver-ts to npm, I'm here to ask that are you will to make a separate PR to the new repository? Or can I cherry pick your commit into my repository?

[teoxoy]

@JounQin I think you can just merge it from upstream.

[JounQin]

@teoxoy Your PR has some conflicts with #20 what makes merging from upstream a bit painful.

[teoxoy]

I will start a PR on your fork then. Let me know when it's ready.

[JounQin]

@teoxoy It's already for a while, please try the repository link above.