Change gamemode switching to use commands (.creative/.survival) instead of keybinding

Update voxel-commands, voxel-gamemode

deathcap/voxel-commands@4d5f5b71deed80c9becb1b06bdacc4643e652b69 Add registerCommand() API
deathcap/voxel-gamemode@4cfd71723fdbf53b5230b1b87a4b2bb3a843aa76 Add .creative/.survival commands, remove keybinding

Commit message generated by https://github.com/deathcap/lmno-cl

Ref https://github.com/deathcap/voxel-gamemode/issues/2