Add Manifest as a backend starter #79

Manifest is the fastest and easiest way to ship a backend. It’s Open Source.

Developers just have to describe their project in a single file and instantly get a complete backend with logic, storage, data, and an admin panel.

Manifest users already use StackBlitz to prototype and test projects with Manifest. Official integration would make this experience even more seamless.

Here’s why it makes sense:

• Our technology uses a simple DSL and SQLite by default, making backends fully portable and able to run directly inside StackBlitz without external dependencies.

• We focus on a "simple code over low-code" philosophy. Manifest is for developers who want to ship production backends fast, not for non-technical users building prototypes. With Manifest, devs can build and ship full backends in under 5 minutes, enabling truly fullstack apps on StackBlitz in record time.

Manifest demo : https://manifest.new
Manifest Open Source repo: https://github.com/mnfst/manifest/tree/master/examples/main-demo