Add the 0.24.0 Unity WebGL players

Built from ReactUnity/core kitchen-sink, WebInjectable and Previewer
profiles. Gzip with decompressionFallback, so the three big files are
.unityweb and the loader inflates them: ~26 MB per player against ~82 MB
raw, and no Content-Encoding header to set -- which Pages cannot do.

WebInjectable.loader.js is replaced, the rest is new alongside the old
plain and .gz files. Those stay until @reactunity/scripts 0.23.2, which
still loads previewer/0.20.0, is out of circulation.

Author: gkurt