* [nix] Update nixpkgs to avoid issues with Big Sur
The older nixpkgs snapshot did not contain nix changes to the
compiler/linker hooks that are necessary for compatibility with MacOS
Big Sur. The fix is simply to update to a newer snapshot.
* [nix] Add a poetry manifest and use poetry to build the Python env
* [nix] Use niv to manage upstream sources like nixpkgs
* [nix] Update to newer nixpkgs snapshot
* [nix] Bump python package versions
* Remove obsolete note about media keys in MacOS
KC_MNXT and KC_MPRV work fine on MacOS, so this note is obsolete.
* Document behaviour of MEDIA_FAST_FORWARD/MEDIA_REWIND codes on MacOS
* Small typo fix, and make OS-dependent keycode claim less absolute
* Update docs/keycodes_basic.md
Co-Authored-By: fauxpark <fauxpark@gmail.com>