[FIX] Add "types" to the "exports" section of package.json

[jkonowitch]

When using "module": "NodeNext", Typescript expects to find a "types" property in the package.json "exports" declaration - see docs.

Because slimdom.js does not, I receive this error.

Could not find a declaration file for module 'slimdom'. '/node_modules/.pnpm/[email protected]/node_modules/slimdom/dist/slimdom.esm.js' implicitly has an 'any' type.
  There are types at '/node_modules/slimdom/dist/slimdom.d.ts', but this result could not be resolved when respecting package.json "exports". The 'slimdom' library may need to update its package.json or typings.ts

I have tested this locally, and this resolves the issue.

[bwrrp]

Awesome, thanks for figuring this out!