Update to the latest Docusaurus version. (2.0.0-beta.17)

[abhigyantrips]

It's that time again. This one introduces a bunch of features that'd refresh the look of the site.

The important new features:

• The theme toggle/slider has been replaced by a theme button, which takes up less space and matches the curvature of the search bar (It looks better, trust me.)
• Breadcrumbs show the structure/location of the pages - like a mini directory structure at the top.
• An option to disable the search page located at https://guide.disnake.dev/search. I think it's a good idea to do that, but this is open to discussion.

Breaking changes? Yes:

• Since the theme toggle is now a button, there is no need of a switchConfig.
• All swizzled components will need to be re-swizzled and re-customized.

Should be a pretty easy task to resolve those. There were also a bunch of bugfixes that would polish things up.

[abhigyantrips]

All of this is covered at https://docusaurus.io/changelog/2.0.0-beta.17. We didn't bump to beta.16 first, so have a look at that as well.