smath-studio: add meta and fix deprecation warning

packages/smath-studio.nix

@@ -1,4 +1,5 @@
 {
+  lib,
   appimageTools,
   fetchurl,
   libgdiplus,
@@ -7,11 +8,12 @@
   version = "1.5.0.9678";
 
   src = fetchurl {
+    # The code after /Download/ changes per release
     url = "https://smath.com/en-US/files/Download/c4zCE/SMathStudioDesktop.1_5_0_9678.x86_64.ubuntu-22_04.glibc2.35.AppImage";
     hash = "sha256-6lnuRnhoH6E+jIZXSgb/Pz9wE9nVAbduDHrkKCKKH+Y=";
   };
 
-  appimageContents = appimageTools.extractType2 {
+  appimageContents = appimageTools.extract {
     inherit pname version src;
   };
 in
@@ -39,4 +41,13 @@ in
         fi
       done
     '';
+
+    meta = with lib; {
+      description = "Tiny, powerful, free mathematical program with WYSIWYG editor and complete units of measurements support";
+      homepage = "https://smath.com/";
+      license = licenses.unfree; # SMath is freeware, but closed source
+      # maintainers = with maintainers; [frajul];
+      mainProgram = "smath-studio";
+      platforms = ["x86_64-linux"];
+    };
   }