Add close button.

[igalklebanov]

Hey 👋

Currently after closing the browser tab manually, users are also required to get back to the terminal and exit the Studio server process.

Would be a nice QoL improvement to add a close button in the CLI distribution that:

1. sends a shutdown request to the Studio server.
2. closes the current browser tab.

[sorenbs]

Hey @igalklebanov 👋 Still a good idea. It splits into two parts: a shutdown endpoint in the CLI's Studio server (prisma/prisma) and the button/affordance in studio-core that calls it and closes the tab. Keeping this open here to track the studio-core half; we'll line up the CLI piece alongside it.