Fixup package.json
Fixup package.json

 - Add explicit "types" field. (with local testing, just putting a file in `dist/index.d.ts` seemed to work, but doesn't when installed - better to be safe than sorry)
 - Explicitly include only `dist` folder in the npm package (we don't need sources, build scripts, etc. to be downloaded by all users).

GoogleChromeLabs/wasm-feature-detect