add .gitignore and opencode path

.gitignore

···
+.crush/*

lib/shared/home.nix

···
   ] ++ lib.optionals pkgs.stdenv.isDarwin [
     "/opt/homebrew/opt/node@22/bin"
     "/opt/homebrew/bin"
+    "$HOME/.opencode/bin"
   ];
   # environment.pathsToLink = ["/usr/share/zsh/vendor-completions"];