Create mapping option

[alvaromontoro]

Is your feature request related to a problem? Please describe.
Right now, if the gamepad is not "standard", the developers have to create their own mapping functionality manually, which is not ideal.

Describe the solution you'd like
Provide developers with an internal functionality to remap buttons/axes.

Describe alternatives you've considered
Create a mapping array/object, and allow developers to set it up. They will still have to figure out a way to display to the user the mapping selection. But once it's done, passing the new mapping array/object should internally fix the mapping.

[gamebrina]

Hey @alvaromontoro I just started a project and found your very nice library. Good work!
I can really use this feature, so I thought I give it a shot myself. You can have a look at my personal changes here:
ae69a4d

Feel free to merge / change or do nothing.

Kind regards, Mark

[alvaromontoro]

Sorry for the late response. I'll check the changes later today. This would be a cool feature to add, thanks! :)