Added some missing #include guards (#64)

headers/bitmaps.h

@@ -1,3 +1,6 @@
+#ifndef BITMAPS_H_
+#define BITMAPS_H_
+
 // bitmaps.h allows you change what is shown on the display during the startup of GP2040.
 // The default image size is 128x64px.
 // The default image type is 2 color monotone (black and white).
@@ -460,4 +463,6 @@ const unsigned char splashImageLegacy[] = {
     0x00, 0x00, 0x00, 0x7f, 0xe7, 0x80, 0x1f, 0xfe, 0x1f, 0xc0, 0x03, 0xc3, 0xf8, 0x00, 0x00, 0x00, 
     0x00, 0x00, 0x00, 0x3f, 0x87, 0x80, 0x1f, 0xfe, 0x0f, 0x80, 0x03, 0xc0, 0xf0, 0x00, 0x00, 0x00, 
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
-};
+};
+
+#endif

headers/songs.h

@@ -1,3 +1,6 @@
+#ifndef SONGS_H_
+#define SONGS_H_
+
 #include "addons/buzzerspeaker.h"
 
 // Intro example
@@ -32,4 +35,6 @@ Song configModeSong{
         FS5,
         E5
     }
-};
+};
+
+#endif