Add package to flake

.gitignore

@@ -320,3 +320,7 @@ TSWLatexianTemp*
 
 ### lualatex ###
 luatex.*/
+
+### Nix ###
+result
+result/

flake.nix

@@ -1,19 +1,60 @@
 {
-description = "LaTeX Beamer Presentation for GPUL Schools: Software Libre";
+  description = "LaTeX Beamer Presentation for GPUL Schools: Software Libre";
   inputs = {
     nixpkgs.url = github:NixOS/nixpkgs/nixos-25.05;
     flake-utils.url = github:numtide/flake-utils;
   };
 
-  outputs = { self, nixpkgs, flake-utils }:
+  outputs = {
-    flake-utils.lib.eachDefaultSystem (system:
+    self,
-      let pkgs = nixpkgs.legacyPackages.${system}; in
+    nixpkgs,
-      {
+    flake-utils,
+  }:
+    flake-utils.lib.eachDefaultSystem (
+      system: let
+        pkgs = nixpkgs.legacyPackages.${system};
+        tex = pkgs.texlive.combine {
+          inherit
+            (pkgs.texlive)
+            scheme-basic
+            latex-bin
+            latexmk
+            collection-langspanish
+            beamer
+            biblatex
+            biber
+            csquotes
+            emoji
+            fontspec
+            noto-emoji
+            ;
+        };
+        # tex = pkgs.texliveFull;
+      in rec {
+        packages = {
+          document = pkgs.stdenvNoCC.mkDerivation rec {
+            name = "latex-beamer-gpul-schools-software-libre";
+            src = self;
+            buildInputs = [pkgs.coreutils tex];
+            phases = ["unpackPhase" "buildPhase" "installPhase"];
+            buildPhase = ''
+              export PATH="${pkgs.lib.makeBinPath buildInputs}";
+              env TEXMFVAR=$(mktemp -d) \
+                SOURCE_DATE_EPOCH=${toString self.lastModified} \
+                latexmk -interaction=nonstopmode -pdf -lualatex \
+                -pretex="\pdfvariable suppressoptionalinfo 512\relax" \
+                -usepretex main.tex
+            '';
+            installPhase = ''
+              mkdir -p $out
+              cp main.pdf $out/
+            '';
+          };
+        };
+        defaultPackage = packages.document;
+
         devShells.default = pkgs.mkShell {
-          buildInputs = with pkgs; [
+          buildInputs = packages.document.buildInputs;
-            texstudio
-            texlive.combined.scheme-full
-          ];
         };
       }
     );