Restructure the codebase across more files.

right/usb_interface_keyboard.h

@@ -0,0 +1,21 @@
+#ifndef __USB_DEVICE_HID_KEYBOARD_H__
+#define __USB_DEVICE_HID_KEYBOARD_H__
+
+// Macros:
+
+    #define USB_KEYBOARD_REPORT_LENGTH (0x08U)
+
+// Typedefs:
+
+    typedef struct _usb_device_hid_keyboard_struct {
+        uint8_t buffer[USB_KEYBOARD_REPORT_LENGTH];
+        uint8_t idleRate;
+    } usb_device_hid_keyboard_struct_t;
+
+// Functions:
+
+    extern usb_status_t UsbKeyboardCallback(class_handle_t handle, uint32_t event, void *param);
+    extern usb_status_t UsbKeyboardSetConfiguration(class_handle_t handle, uint8_t configuration);
+    extern usb_status_t UsbKeyboardSetInterface(class_handle_t handle, uint8_t interface, uint8_t alternateSetting);
+
+#endif