Gets an actor by its tags, creating it if necessary.
Examples
Example 1
const room = await client.get<ChatRoom>({
name: 'chat_room',
// Get or create the actor for the channel `random`
channel: 'random'
});
// This actor will have the tags: { name: 'chat_room', channel: 'random' }
await room.sendMessage('Hello, world!');