Add gyro aiming support

[blakeplusplus]

Feature Request

I've searched in both the Discord, xemu/issues, xemu/pulls, and the docs for mention of gyro or gyroscope support; couldn't find anything.

Gyro aim is a form of fine control analog aiming using a gyroscope built into some controllers that many prefer over regular analog sticks. Regular analog sticks have issues with precision that is usually aided by some form of aim assist to your target. Gyro aim can make aiming feel fluid and precise without relying on possibly poor in-game aim assist (or sometimes games don't even have aim assist).

Here's a list of emulators that support gyro.

Alternatives

Mouse support would be great (I believe there's a PR open right now), but that requires using a mouse. If you want to use a controller but also have the precision of mouse aim, you have to use gyro. For an example, using mouse and keyboard in Ninja Gaiden Black would be a nightmare, but using a controller and having gyro control for the moments you do have to aim would be great!

I believe you can also launch xemu through Steam, and then implement gyro aim through Steam Input? Not sure, haven't tested it. I think relying on proprietary software outside the emulator isn't something that should be aimed for long-term, but short-term, if it works that's awesome.

JoyShockMapper is also available and is FOSS, but it currently has limited/nonexistent support for Linux/macOS respectively.

Additional Context

While implementing gyro aim at all would be great, the way it would be implemented needs to be thought of. Gyro aim is often at its best when mixed with analog stick aiming. Gyro is great for small, precise movements, while sticks are great for large, sweeping movements. Some may also desire gyro aim being on at all times.