Update TypeScript exports to support moduleResolution bundler

[kwangure]

moduleResolution: "bundler" is a recent setting added to TypeScript to support bundler setups. It's the setting you should probably be using when bundling code. With this setting TypeScript only searches for types in the exports field of the package.json.

It requires the following change:

 "exports": {
   "import": "./dist/index.js",
   "require": "./dist/index.cjs",
+  "types": "./dist/index.d.ts"
 },

This is issue is relevent to multiple @lezer packages I'm using.

[marijnh]

Should be handled by 339111b