adding support for custom ca certificate

Hello,

For now if I have self-signed certificate in the system CA, `urllib` doesn't recognize it and model download by ComfyUI-Manager doesn't work.
I figure out that I can set up `bypass_ssl = True` in the `config.ini` file, which doesn't check ssl during model download.

However for the sake of security, would it be possible to add option in `config.ini` file such that ComfyUI-Manager can use the specified ca-certificate?

Thanks