[Feature/1149] Dark mode: functions for manually switching theme (#1291)

* [Feature/1149] Dark mode: functions for manually switching theme

v2/internal/frontend/devserver/devserver.go

@@ -47,6 +47,18 @@ type DevWebServer struct {
 	devServerAddr string
 }
 
+func (d *DevWebServer) WindowSetSystemDefaultTheme() {
+	d.desktopFrontend.WindowSetSystemDefaultTheme()
+}
+
+func (d *DevWebServer) WindowSetLightTheme() {
+	d.desktopFrontend.WindowSetLightTheme()
+}
+
+func (d *DevWebServer) WindowSetDarkTheme() {
+	d.desktopFrontend.WindowSetDarkTheme()
+}
+
 func (d *DevWebServer) Run(ctx context.Context) error {
 	d.ctx = ctx