Joystick: add support for 8-way hat switch

[fauxpark]

Description

Hat switches function a little differently to regular joystick axes, in that they have a "null" state rather than always having a value. Therefore it cannot simply be added by increasing the axis count.

Currently the report descriptor has been set up for an 8-way hat switch, but this could potentially be increased to anything that divides evenly into 360 and gives a maximum angle that is a whole number (so not 16-way as the pitch is 22.5 degrees and the max angle is 337.5). I've not checked whether the physical min/max tags are necessary so maybe this restriction is irrelevant.

Tested on Proton-C, V-USB not tested but should work too.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).