Adding support for Chatter keypad (#4022)

* Adding support for Chatter keypad

* Remove user button mapping since full keypad is now useable

* Adding TAB key and RIGHT to allow selecting a destination

* Fix shift bug (there's only three levels, not four)

* reformat file

* Fix bug with fast repeated keypresses

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/input/SerialKeyboardImpl.cpp

@@ -0,0 +1,21 @@
+#include "configuration.h"
+#include "InputBroker.h"
+#include "SerialKeyboardImpl.h"
+
+#ifdef INPUTBROKER_SERIAL_TYPE
+
+SerialKeyboardImpl *aSerialKeyboardImpl;
+
+SerialKeyboardImpl::SerialKeyboardImpl() : SerialKeyboard("serialKB") {}
+
+void SerialKeyboardImpl::init()
+{
+    if (!INPUTBROKER_SERIAL_TYPE) {
+        disable();
+        return;
+    }
+
+    inputBroker->registerSource(this);
+}
+
+#endif // INPUTBROKER_SERIAL_TYPE