Ability to use TTL on Maps

The default store is `new Map()`. It has no(?) TTL support. But we could do something like:

```js
if (store instanceof Map) {
	store.timers = {};
	store._set = store.set;
	store.set = (key, value, ttl) => {
		clearTimeout(store.timers[key]);
		store.set(key, value);
		store.timers[key] = setTimeout(() => {
			delete store.timers[key];
			store.delete(key);
		}, ttl);
	};
}
```