Add page on controller-specific features (currently just LED)

[Meorge]

Sets the groundwork and first feature for #11466 .

This PR adds a new page, "Controller features", which describes and provides examples for various controller features that are less essential than "Controllers, gamepads, and joysticks".

Currently, because LED light control is the only merged feature so far, it is the only section on the page; however, as other features like adaptive triggers, touchpads, accelerometer and gyroscope, and joypad information are added to the engine, corresponding sections on these features can be added to this page.

[Meorge]

If anyone has a good camera setup that would allow them to record a DualSense/DualShock controller's LEDs, perhaps that looks a bit like this:

I think that would make a great addition to the code samples, so people could see how it looks in practice without needing to set up their own project 😄