Readme and resources update

[TheDuckCow]

No functional changes, routine auto updates and text improvements.

[TheDuckCow]

Welp, so much for being a safe update. Apparently minecraft renamed grass ie upright grass texture) to colormap/grass and on top of that, for some reason the texture isn't getting saturated/color tinted like it should. Being such a central texture, used for meshswapping.

It means we need to decide whether to rename the actual texture / object name within meshswap for grass, or whether to create an inserted fake mapping for that object in our mapping file. I need to contemplate this.

Edit: The two tests broken by this are test_meshswap_world_mineways_separated (subtest [grass]) and test_canonical_test_mappings