feat: track current game mode config index

Track index of current game mode config to prevent switching from one
GameModeConfig to the same GameModeConfig, which in turn prevents
spamming of keypresses when entering a keyboard mode on RP2040.

Closes #21

src/core/mode_selection.cpp

@@ -13,6 +13,8 @@
 
 uint64_t mode_activation_masks[sizeof(Config::game_mode_configs) / sizeof(GameModeConfig)];
 
+size_t current_mode_index = 0;
+
 void set_mode(CommunicationBackend *backend, ControllerMode *mode) {
     // Delete keyboard mode in case one is set, so we don't end up getting both controller and
     // keyboard inputs.
@@ -107,7 +109,8 @@ void select_mode(
 
     for (size_t i = 0; i < mode_configs_count; i++) {
         const GameModeConfig &mode_config = mode_configs[i];
-        if (all_buttons_held(inputs.buttons, mode_activation_masks[i])) {
+        if (all_buttons_held(inputs.buttons, mode_activation_masks[i]) && i != current_mode_index) {
+            current_mode_index = i;
             set_mode(backend, mode_config, keyboard_modes, keyboard_modes_count);
             return;
         }