WEB: Add code highlighting in PDEPs and render tables correctly
- [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Discovered that tables were rendering really nastily and there was no code highlighting so PDEPs were looking a little bland while working on PDEP 7.

Note: The codehilite.css file that I added was generated by pygments, and is based on the ``friendly`` style
(I'll try to find the pydata-sphinx-theme style css file though).
Nvm, we basically have the same thing as pydata-sphinx-theme, the only difference is that we don't have the box around the code block so it still looks kinda nasty. <img width="539" alt="image" src="https://user-images.githubusercontent.com/47963215/219721819-ae8bb99f-7d7c-46ae-8479-7f15399ece77.png">

This is what it looks like. We clearly have been noticing the same things ;) The last days, I was thinking we could also use sphinx (with myst) instead to solve many of those issues. I wrote up https://github.com/pandas-dev/pandas/issues/51461 about that Preview docs at: https://pandas.pydata.org/preview/51458/ Looks like you're changing the background color of the navigation bar, not sure if that's intended. I like how it looks like actually, but feels like this PR shouldn't change it, right?

Also, we can address it in a follow up PR, but I think we can add some padding and maybe a border to the code boxes: https://pandas.pydata.org/preview/51458/pdeps/0004-consistent-to-datetime-parsing.html

Happy to take care of that myself in a follow up PR, but probably easy to add it here too. > Looks like you're changing the background color of the navigation bar, not sure if that's intended. I like how it looks like actually, but feels like this PR shouldn't change it, right?

My bad. Just realized now that I'm in a different monitor, where the color looks darker. Interesting that everything else looks the same, except of our navigation bar. Sorry about the noise. > Also, we can address it in a follow up PR, but I think we can add some padding and maybe a border to the code boxes: https://pandas.pydata.org/preview/51458/pdeps/0004-consistent-to-datetime-parsing.html

Thanks @lithomas1. I think we can address the above comment in a follow up, but nice improvement to the website!