Add "types" to package.json exports to fix module type resolution

[trevorsmith]

This commit fixes the following Typescript error:

Could not find a declaration file for module 'urlcat'. 'foo/node_modules/urlcat/dist/index.mjs' implicitly has an 'any' type.
There are types at 'foo/urlcat/dist/index.d.ts', but this result could not be resolved when respecting package.json "exports". The 'urlcat' library may need to update its package.json or typings.