ironbar: Add overview button for hycov

Note that on_mouse_enter is used instead of on_click_left to avoid an
issue where the focus of hycov is lost after clicking on the bar.

home/ironbar.nix

@@ -55,6 +55,12 @@
         {
           "type": "clock",
           "format": "%x（%a）%R"
+        },
+        {
+          "name": "overview",
+          "type": "label",
+          "label": "🅰",
+          "on_mouse_enter": "hyprctl dispatch hycov:toggleoverview"
         }
       ]
     }
@@ -146,5 +152,10 @@
       padding-left: 1em;
       padding-right: 0.5em;
     }
+
+    #overview {
+      padding-left: 0.5em;
+      padding-right: 1em;
+    }
   '';
 }