Adds devcontainer and Autogenerated Docs

[avb-is-me]

Describe Your Changes

-Add .devcontainer starter json with node:20 so people can run on codespaces and devpod. Electron does not work great on codespaces, but the server and other aspects run fine.

-Adds Autogenerated Docs for how to use the local API server. All the Docs are AI generated without refinement and I added the _ in front of them so you can delete, keep, or remove the underscore if you want to show the documentation. I am sure these docs are not perfect but would love to get your feedback on some of them, or any improvements I can make to help the team save time and energy writing docs from scratch.

[avb-is-me]

@hieu-jan I'll try to divide into different pull requests

[avb-is-me]

@hieu-jan https://github.com/janhq/jan/pull/1739

[henryh0x1]

Hi @avb-is-me, I merged your separated PR of devcointainer.json. Thank you so much for your contribution. For API Reference, I also updated https://jan.ai/api-reference/ with the input and output of real example for current Jan server. Feel free to made any pull request to modify this page if you find any bugs.