DOC: add button to edit on GitHub

[DoNguyenHung]

• closes DOC: add button to edit on GitHub #39859
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations 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.

Changes made:

• Added an extension that allows to have a sidebar with extra "Show on GitHub" and "Edit on GitHub" links. Found here.
• Modified conf.py to make sure the extension is added and links direct to editable pages.

[DoNguyenHung]

Hi mroeschke, would you mind taking a look at this? My fix should have all the links direct-able and I added an extension so it resembles the issue description #39859. This is my first issue so please let me know if there's any convention I'm missing. Also, I said in the issue that I was working on this, but I had a ton of issues building pandas for the first time, so that's why my update is delayed. Thanks in advance!

[DoNguyenHung]

pre-commit.ci autofix

[mroeschke]

Thanks for the PR, but someone is already working on this in #61956 so closing to let them have a change to finish. But happy to have contributions labeled good first issue that doesn't have a linked PR open