Secrets support for tools

[tarasglek]

I would like to use chatcraft as a convenient UI to call APIs. Those APIs have secrets. Need something like cloudflare env vars for secrets.

I imagine the flow to be like this:

1. I write myself a system prompt and a gist to convert pdfs to markdown using https://mathpix.com/docs/ocr/creating-an-api-key

2)the gist will declare dependency on process.env.MATHPIX_OCR_API_KEY

3)When we issue the function call, chatcraft will issue error "please enter key MATHPIX_OCR_API_KEY in options dialog", pop up options.

4)We have a UI in options that lets one enter keys, keys are only saved in localstorage

5. We can now safely share chatcraft chats with tool-using secret-requiring system prompts