Define and apply matcher :be_rendered

Add this changes to make components specs clear

spec/components/layout/locale_switcher_component_spec.rb

@@ -13,7 +13,7 @@ describe Layout::LocaleSwitcherComponent do
     it "doesn't render anything" do
       render_inline component
 
-      expect(page.native.inner_html).to be_empty
+      expect(page).not_to be_rendered
     end
   end