python-docs-theme ui is make reading hard.

[neuralstring]

After reading rust-lang book, I came to python docs and man it's ugly and painful to read.
Lacking dark-mod, improper separation of heading, bad color scheme and more...

With little CSS changes, I made it more comfortable for myself,
If you agree to apply these changes to the main repo, I can send a push request.
Here is my changes:

Before:

After:

[ezio-melotti]

This looks like a duplicate of #43 (which also has a PR: #44).

[sylv256]

Could you send the CSS for this for others to use?

[pradyunsg]

Consolidating into #43.