config screen: added const specifier to some class variables

ConfigurationScreen.h

@@ -9,10 +9,10 @@ class ConfigurationScreen : public Screen
 
 public:
 
-    midi::Launchpad::KeyCoordinate configWidth = midi::Launchpad::width - 1;
-    Player::Bpm minBpm = 1;
-    Player::Bpm maxBpm = (1 << (configWidth * 2)) - 1;
-    BeatIndex maxBeatsCount = (1 << configWidth) - 1;
+    const midi::Launchpad::KeyCoordinate configWidth = midi::Launchpad::width - 1;
+    const Player::Bpm minBpm = 1;
+    const Player::Bpm maxBpm = (1 << (configWidth * 2)) - 1;
+    const BeatIndex maxBeatsCount = (1 << configWidth) - 1;
 
     ConfigurationScreen(Sequencer& seq);