add keyboard interface (#95)

hid/lib/drivers/keyboard.h

@@ -26,9 +26,41 @@
 
 namespace DRIVERS {
 
-    typedef struct {
-        bool caps;
-        bool scroll;
-        bool num;
-    } KeyboardLedsState;
+	typedef struct {
+		bool caps;
+		bool scroll;
+		bool num;
+	} KeyboardLedsState;
+
+
+	struct Keyboard : public Driver {
+		using Driver::Driver;
+		
+		virtual void begin() {}
+	
+		/**
+		* Release all keys
+		*/
+		virtual void clear() {}
+	
+		/**
+		* Sends key
+		* @param code ???
+		* @param state true pressed, false released
+		*/
+		virtual void sendKey(uint8_t code, bool state) {}
+	
+		virtual void periodic() {}
+	
+		/**
+		* False if online or unknown. Otherwise true.
+		*/
+		virtual bool isOffline() { return false; }
+	
+		virtual KeyboardLedsState getLeds() {
+			KeyboardLedsState result = {};
+			return result;
+		}
+
+	};
 }