add modrinth handler and some other tweaks

modules/home/misc/scheme-handlers.nix

@@ -0,0 +1,18 @@
+{ pkgs, ... }:
+let
+  ferium-installer-script = pkgs.writeShellScript "ferium-installer" ''
+    mod=$(echo "$1" | awk -F'/' '{print $NF}')
+    ${pkgs.kitty}/bin/kitty sh -c "ferium add $mod; read"
+  '';
+in
+{
+  xdg.desktopEntries."ferium-installer" = {
+    name = "Intercept Modrinth Links to Ferium";
+    exec = "${ferium-installer-script} %u";
+    mimeType = [ "x-scheme-handler/modrinth" ];
+  };
+
+  xdg.mimeApps.defaultApplications = {
+    "x-scheme-handler/modrinth" = "ferium-installer.desktop";
+  }; 
+}