Secure storage for keys in chatcraft

[tarasglek]

I believe we want something like origin-isolated storage.

Some notes in https://chatcraft.org/api/share/tarasglek/20XBZ-vNRsH6R5s4bchKP.

I think we should have an iframe that

• Allows one to add provider (with api key
• Allows one to update api keys
• allows listing providers(while withholding api key)
• provides an api that can proxy fetch() calls and inject the bearer token

Basically it should serve as write-only way to store keys, while allowing some read metadata. This way any generated or otherwise injected code can't access our precious keys.