Added Alpha Numeric Mappings

GLFW key mappings where added for ease of reference.

src/raylib.h

@@ -117,6 +117,45 @@
 #define KEY_RIGHT_CONTROL   345
 #define KEY_RIGHT_ALT       346
 
+// Keyboard Alhpa Numeric Keys
+#define KEY_ZERO             48
+#define KEY_ONE              49
+#define KEY_TWO              50
+#define KEY_THREE            51
+#define KEY_FOUR             52
+#define KEY_FIVE             53
+#define KEY_SIX              54
+#define KEY_SEVEN            55
+#define KEY_EIGHT            56
+#define KEY_NINE             57
+#define KEY_A                65
+#define KEY_B                66
+#define KEY_C                67
+#define KEY_D                68
+#define KEY_E                69
+#define KEY_F                70
+#define KEY_G                71
+#define KEY_H                72
+#define KEY_I                73
+#define KEY_J                74
+#define KEY_K                75
+#define KEY_L                76
+#define KEY_M                77
+#define KEY_N                78
+#define KEY_O                79
+#define KEY_P                80
+#define KEY_Q                81
+#define KEY_R                82
+#define KEY_S                83
+#define KEY_T                84
+#define KEY_U                85
+#define KEY_V                86
+#define KEY_W                87
+#define KEY_X                88
+#define KEY_Y                89
+#define KEY_Z                90
+
+
 // Mouse Buttons
 #define MOUSE_LEFT_BUTTON     0
 #define MOUSE_RIGHT_BUTTON    1