Add migration for new ristretto theme

migrations/1753689791.sh

@@ -0,0 +1,5 @@
+echo "Add the new ristretto theme as an option"
+
+if [[ ! -L ~/.config/omarchy/themes/ristretto ]]; then
+  ln -nfs ~/.local/share/omarchy/themes/ristretto ~/.config/omarchy/themes/
+fi