Update refs and fix extensions docs.

Update build-and-test.yml

Merge pull request SixLabors#136 from SixLabors/js/fix-lfs

Fixes missing LFS pointers for images

Merge pull request SixLabors#135 from SixLabors/js/beta-12

Update refs and tests to match latest NuGet.

Merge pull request SixLabors#96 from SixLabors/af/polygon-lab

Fast polygon scanning with active edge list

Merge pull request SixLabors#62 from SixLabors/js/beta-10

Beta 10

Merge pull request SixLabors#53 from SixLabors/js/apache

Update license, config and docs.

Merge pull request SixLabors#45 from SixLabors/sw/beta-8

Update licence to AGPL 3 & update Fonts dependency

Merge pull request #993 from SixLabors/js/update-submodule

Beta7

Update dependencies + fix stylecop (#816)