TextEditor: Select everything in the find textbox when pressing Ctrl+F

This allows you to press Ctrl+F and immediately start typing a new
search string, instead of having to remove the old one first. :^)

Applications/TextEditor/TextEditorWidget.cpp

@@ -92,6 +92,7 @@ TextEditorWidget::TextEditorWidget()
     m_find_action = GAction::create("Find...", { Mod_Ctrl, Key_F }, [this](auto&) {
         m_find_widget->set_visible(true);
         m_find_textbox->set_focus(true);
+        m_find_textbox->select_all();
     });
 
     m_editor->add_custom_context_menu_action(*m_find_action);