Add type: commonjs package.json to cjs output

[dgreif]

After #9, we have both commonJS and esm. When imported from commonjs, it will resolve the cjs files, but it iterprets them as esm because the nearest package.json is type: module

To fix this, we can add a new package.json in dist/cjs with { "type": "commonjs" } to hint to node that the code is indeed cjs

Big thanks to @calebboyd for pointing this out!

[jfuchs]

😅 good catch