Documentation UX improvements ideas

Hi,

I had some trouble recently reading Hugging Face documentation, specifically the API reference section, and thought I would share my ideas:

For better explanation, here is comparison of pandas reference documentation

I personally, find the Pandas documentation much easier to read.

Specific moves to make it more readable IMHO:

- Split each function into it's own page OR at least add the functions to the right hand sidebar
- Remove the pollution of guides and tutorials, and installation instructions from the API reference sidebar

And maybe:

- Increase the contrast, especially of the argument types and default values
- Increase the prominence of the functions and classes, right now, they "feel" less visible than the text they are supposed to be heading
- Increase the width of the main content - cover more screen space
- Increase the line spacing - better readability