Add storage adapters

## About

It would be nice to add support multiple storage mechanisms.

Example

```js
import { createInstance } from 'subscriptionless';
import { DynamoDBPersistence } from 'subscriptionless/dynamodb';

const instance = createInstance({
schema,
storage: DynamoDBPersistence({
dynamodb,
tableNames: {
connections: 'my_connections'
}
})
});
```

## Notes

Whether this is of any value still remains to be seen.

**Drop a comment** if you have a use case where something other than DynamoDB would be of use.