Add index.html and code.html to repo

[SuperGamer001]

I need to add files so users can test if Gamepad.js works on their device.

• index.html - This page shows you how many buttons and axes your connected controller has, and their values (pressed, axis rotation, pressure on press, controller rotation etc.).

• code.html - Here is where you can help out. This asks you questions about where buttons and axes are. You answer by pressing or moving the specified input, and the project will write code for you to submit to the Discussions area of this repo.