Emscripten gamepad event class draft

[Jonathhhan]

I tried to make a class for gamepad events, maybe its better than to include everything in ofxAppEmscriptenWindow.
Just add #include ofxEmscriptenGamePad.h to ofApp.h and call gamepad.gamePadData() in ofUpdate() for updating the gamepad events. Just need to find a way how to return the data, maybe someone has an idea?
This is why I closed this PR (there is some information about gamepad events and how I adapted them): #7243
But the event array I mention there, thats also included in this class, could be useful for other events, too.
What do you think about that approach @ofTheo? A similar thing could be done for the webMidi stuff...
And maybe someone wants to optimize the class, if it is a good approach, because I am really not experienced in making classes ;)

[Jonathhhan]

Another idea is to make one class (ofxEmscriptenEvents for example) that holds all Emscripten events, that are not connectet to ofBaseEvents. This way, I would know how to pass the values to ofApp.cpp(edit: actually not true, yet)...