Add a README.md section on how to setup the import rules in your project, depending on what bundler you're using.

[ThijsTyZ]

We might need a section on how to setup the import rules in your project, depending on what bundler you're using:

• node (I think works by default)
• js (I think works by default)
• webpack (requires config in your project)
• pure TS (requires config in your project - or could be included in this package if we choose to, is another comment)
• what about parcel/rollup/etc?

If the user doesn't do this, the project will report errors on all imports that are not node/node_modules.

Originally posted by @ThaNarie in #6 (comment)