[feature request] untangle `gradio` dependency from minichain "core"

[samuela]

gradio is a fairly heavyweight dependency and may not be necessary in production deployments. currently, import minichain requires gradio to be installed via

https://github.com/srush/MiniChain/blob/b79ebc51bdedb836c9265eec2fcc21cd60b17327/minichain/init.py#L16

and

https://github.com/srush/MiniChain/blob/b79ebc51bdedb836c9265eec2fcc21cd60b17327/minichain/gradio.py#L6

would it be possible to untangle gradio from minichain core and make it optional? more generally, would it be possible to build a minichain "core" which additional components then build off of?