Implement Indexed DB wrapper API

[romandev]

The API set should include the following things at least:

[
  Constructor(string dbName)
]
interface IndexedDB {
  Promise<void> set(string key, object value);
  Promise<object> get(string key);
  Promise<object> remove(string key);
};

[romandev]

@yeonsuyam Hi, are you working on this?

[yeonsuyam]

@romandev
I had a schedule that I had to handle urgently, and I was delayed. Sorry. I will start quickly and let you know the progress.