Made the objectStore, index and cursors generic

[mariusGundersen]

This is a small feature to make the ObjectStore be slightly more strongly-typed. It uses generic methods to add types to the ObjectStore, Index and Cursor, but defaults to any if they are missing (just like today). This means the following code works:

const store = tx.ObjecStore<Person>('people');
const jake = await store.get('Jake');//jake is now of type Person
console.log(jake.name);

[jakearchibald]

I like it! Thank you

[stefan505]

This has not been released yet. Doing an NPM install results in the old idb.d.ts file.