add lean4-nix (#260)

Author: 9glenda

README.md

@@ -26,6 +26,7 @@
     * [Gleam](#gleam)
     * [Haskell](#haskell)
     * [Haxe](#haxe)
+    * [Lean](#lean)
     * [Node.js](#nodejs)
     * [OCaml](#ocaml)
     * [PHP](#php)
@@ -208,6 +209,10 @@
 * [haxix](https://github.com/MadMcCrow/haxix) - Nix flake to build haxe/Heaps.io projects.
 * [kebab](https://github.com/bwkam/kebab) - Haxe packages for Nix.
 
+### Lean
+
+* [lean4-nix](https://github.com/lenianiva/lean4-nix) -  Nix flake build for Lean 4, and `lake2nix`.
+
 ### Node.js
 
 * [Napalm](https://github.com/nix-community/napalm) - Support for building npm packages in Nix with a lightweight npm registry.