i3: set floating modifier to alt

modules/i3/default.nix

@@ -32,6 +32,7 @@ in with theme.colors; {
     config = {
       defaultWorkspace = "workspace number 1"; # defaults to 10 for some reason
       modifier = mod;
+      floating.modifier = "Mod1";
       gaps = {
         inner = 12;
         smartGaps = true;