Accept the image pixel baselines

Captured by the Linux and macOS jobs, which build the shim from source, so they
describe the renderers in this branch rather than the committed binaries.

Both heads draw the two pictures at native size, one blank line under the
property rows, on a checkerboard the transparent half shows through. The byte
counts read the same on all three platforms, which is what SamplePng's stored
deflate blocks are for.

Author: SimonCropp