Number Button Fix

- Add `is_editing` helper to BaseStringButton
- Block left/right input from changing number while typing

Resolves #706

src/dusk/ui/number_button.cpp

@@ -54,7 +54,7 @@ void NumberButton::set_value(Rml::String value) {
 }
 
 bool NumberButton::handle_nav_command(NavCommand cmd) {
-    if (cmd == NavCommand::Left || cmd == NavCommand::Right) {
+    if (!is_editing() && (cmd == NavCommand::Left || cmd == NavCommand::Right)) {
         const int newValue = std::clamp(
             mGetValue() + (cmd == NavCommand::Right ? mStep : -mStep), mMin, mMax);
         if (newValue != mGetValue()) {
@@ -66,4 +66,4 @@ bool NumberButton::handle_nav_command(NavCommand cmd) {
     return BaseStringButton::handle_nav_command(cmd);
 }
 
-}  // namespace dusk::ui
+}  // namespace dusk::ui