Add Made with Lush section to Readme

[rktjmp]

Probably just a short paragraph linking to /made_with_lush/readme.md.

Themes sorted alpha numeric.

Possible contribution guidelines:

• --- or ### theme name
• link in form user/repo
• max ... 50? word description ("Melange is a dark color scheme with a warm, moderate contrast color palette. It supports tree-sitter and regular highlighting (works with Vim8)."
• max two images
  • one showing some consistent code block (part of lush that wont change much?), for more consistent comparison between themes?
  • might not be realistic
  • one showing anything else
  • some reasonable max size (gh caps readme at 900px wide)
  • named __1/2.png

[rktjmp]

a8008d0ff39d9eecc14f63cb099cbf1fd1978ce8