This commit reduces the workgroup shared memory of binning to fit in
16k (by packing two u16's in a u32), and moves the config binding to
uniform, from readonly storage.
Progress toward #202
As stated by the README, the intention is for the shaders to be
provided under the terms of the Unlicense in addition to the MIT
and Apache-2.0 licenses.
While here, add a self-contained UNLICENSE file to replace the
external reference to unlicense.org.