Add Explicit Quit button

Improve UX, to prompt user to explicitly quit and reset state of connected device

Author: rjsmith

src/core.py

@@ -1638,6 +1638,11 @@ def __init__(self):
         self.btn_sharps_flats = pygame_gui.elements.UIButton(
             relative_rect=pygame.Rect((bs.x * 16 + 2, y), (bs.x, bs.y)),
             text='#/b',
+            manager=self.gui  
+        )
+        self.btn_quit = pygame_gui.elements.UIButton(
+            relative_rect=pygame.Rect((bs.x * 17 + 2, y), (bs.x, bs.y)),
+            text='QUIT',
             manager=self.gui
         )
         # self.next_scale = pygame_gui.elements.UIButton(
@@ -2239,6 +2244,8 @@ def logic(self, dt):
                         self.prev_mode()
                     elif ev.ui_element == self.btn_sharps_flats:
                         self.toggle_sharps_flats()
+                    elif ev.ui_element == self.btn_quit:
+                        self.quit()    
                 # elif ev.type == pygame_gui.UI_HORIZONTAL_SLIDER_MOVED:
                 #     if ev.ui_element == self.slider_velocity:
                 #         global self.options.velocity_curve