fix: fix syntax highlighting and update less accurate Bot documentation

[null8626]

Proposed changes:

• Fix syntax highlighting by adding additionalLanguages to the docusaurus configuration file (see https://docusaurus.io/docs/markdown-features/code-blocks).
• Fix the Top.gg tagline showing up as liking dinosaurs for some reason.
• Remove unused image and SVG assets, presumably docusaurus templates.
• Update favicon.ico.
• Mark the search feature as deprecated (Or you can just delete it from the documentation altogether).
• defAvatar CAN return null (try fetching info on newer bots like 1198887580729622599).
  
• Deprecated properties like lib shouldn't show up on example outputs.

Also, the <deprecated /> component doesn't even show up on the website 💀

[pj924]