Define exports.types in package.json

[alexanderl19]

exports.types in package.json is currently missing.

This prevents some bundlers (tested with vite/sveltekit) from properly finding the types for this package despite the types property.

If anyone else is running into this problem, I've aliased poline to the ts file directly in my vite config as a hacky work around. Here's my config:

{
    resolve: {
        alias: {
            poline: './node_modules/poline/src/index.ts',
        },
    },
    ...
}