picom: ignore shadows on i3 tabs

modules/picom/default.nix

@@ -3,6 +3,11 @@
 {
   services.picom = {
     enable = true;
+    shadow = true;
+    shadowOffsets = [
+      (-15)
+      (-15)
+    ];
     settings = {
       backend = "glx"; # Fixes black backdrop on some rounded corners
       corner-radius = 12;
@@ -20,6 +25,9 @@
         "window_type = 'dock'"
         "window_type = 'desktop'"
       ];
+      shadow-exclude = [
+        "class_g = 'i3-frame'"
+      ];
       opacity-rule = [
         "0:_NET_WM_STATE@:32a *= '_NET_WM_STATE_HIDDEN'"
       ];