apprt/gtk: add toggle_maximize keybind and window-maximize config option

src/Surface.zig

@@ -646,6 +646,16 @@ pub fn init(
             // an initial size shouldn't stop our terminal from working.
             log.warn("unable to set initial window size: {s}", .{err});
         };
+
+        if (config.@"window-maximize") {
+            rt_app.performAction(
+                .{ .surface = self },
+                .toggle_maximize,
+                {},
+            ) catch |err| {
+                log.warn("unable to maximize window: {s}", .{err});
+            };
+        }
     }
 
     if (config.title) |title| {
@@ -4168,6 +4178,12 @@ pub fn performBindingAction(self: *Surface, action: input.Binding.Action) !bool
             {},
         ),
 
+        .toggle_maximize => try self.rt_app.performAction(
+            .{ .surface = self },
+            .toggle_maximize,
+            {},
+        ),
+
         .toggle_fullscreen => try self.rt_app.performAction(
             .{ .surface = self },
             .toggle_fullscreen,