HexGL runtime packaged for PLAYCHIVE

Upstream repository: https://github.com/BKcore/HexGL
Pinned revision: 6addc95a2fce3bf05f4d751823cc054c61a16d68
Upstream project: https://hexgl.bkcore.com/

The upstream root LICENSE is MIT. Some individual files retain their own
upstream notices, including bkcore/hexgl/ShipControls.js (CC BY-NC 3.0) and
the audio attribution terms in HEXGL-AUDIO-LICENSE.txt. PLAYCHIVE distributes
this runtime on a non-commercial basis and retains these files verbatim.

Packaging changes: no gameplay files are fetched from third parties at runtime;
the legacy Google Analytics loader and remote favicon references were removed
from the copied index.html. HexGL's game assets, scripts and audio are all
served from this directory.