sdl2-{image,mixer}: add pkgconfig deps

configuration.nix

@@ -16,6 +16,10 @@ final: prev: {
 
   text-icu = prev.callPackage ./pkgs/text-icu.nix { icu-i18n = pkgs.icu; };
 
+  sdl2-image = addPkgconfigDepends prev.sdl2-image [ pkgs.libtiff pkgs.libdeflate pkgs.libwebp ];
+
+  sdl2-mixer = addPkgconfigDepends prev.sdl2-mixer [ pkgs.glib pkgs.pcre2 pkgs.libsndfile pkgs.libpulseaudio pkgs.alsa-lib pkgs.jack2 ];
+
   X11-xft = addPkgconfigDepends prev.X11-xft [ pkgs.expat pkgs.xorg.libXau pkgs.xorg.libXdmcp ];
 
   zlib = prev.callPackage ./pkgs/zlib.nix { inherit (pkgs) zlib; };