feat: add simple fal_client for sync/async + streaming

[isidentical]

stuff we need to do before friday:

• [ ] test this, publish it as a package, change the docs & references in the website to use it

some features to make this complete:

• [ ] Add an easy way to upload files (like fal.toolkit.Image) directly to our CDN or as base64
• [ ] Implement a client for websocket/real-time communication
• [ ] Better error handling