add a .clang-format file (#9154)

src/input/SerialKeyboardImpl.h

@@ -9,11 +9,10 @@
  *      to your device as you wish, but you always need to have separate event
  *      handlers, thus you need to have a RotaryEncoderInterrupt implementation.
  */
-class SerialKeyboardImpl : public SerialKeyboard
-{
-  public:
-    SerialKeyboardImpl();
-    void init();
+class SerialKeyboardImpl : public SerialKeyboard {
+public:
+  SerialKeyboardImpl();
+  void init();
 };
 
 extern SerialKeyboardImpl *aSerialKeyboardImpl;