Screen-brightness-control

* Change return types for `[set/get/fade]_brightness`. They will no longer return `int`, always `List[int]`
* Clean up `fade_brightness` internal error handling
* `linux.XBacklight` now raises `ValueError` if no valid output is received from the command
* Remove deprecated module level variable `method`
* More improvements to the documentation building toolchain

* Simplify `windows.VCP.iter_physical_monitors` `start` kwarg logic
* Actually bump `_version.py` version info this time

* Add missing variable deceleration in `windows.get_display_info`
* Move version info to `_version.py`
* New documentation tool-chain
* Deprecate module level `method` variable

* Fix 13 where some laptop displays were being returned by `windows.VCP.iter_physical_monitors`
* `windows.VCP.iter_physical_monitors` will now only return handles for monitors with the `win32con.DISPLAY_DEVICE_ATTACHED_TO_DESKTOP` StateFlag (see [this comment](https://github.com/Crozzers/screen_brightness_control/issues/13#issuecomment-956567787) for explanation)

* Merge PR 12

* Fix `linux.DDCUtil.set_brightness` expiring non-existent cache keys
* Refactor `linux.XRandr.get_display_info` and `linux.DDCUtil.get_display_info` to be more readable
* All calls to `ddcutil` executable now have stderr suppressed
* Minor optimizations and tweaks to reduce pylint warnings