bump version to v0.5.1

Merge pull request #76 from dloebl/fix-code-scanning-alerts

fix code scanning alerts

Merge pull request #71 from dloebl/backport-fix-32-bit

Backport #70 to v0.4

update README

ci: bump macos runner to macos-11

the macos-10.15 runner has been deprecated

bump to v0.3.1

Merge pull request #50 from dloebl/interlaced

Add support for interlaced encoding

bump version

Merge pull request #42 from MCLoebl/add_test_with_more_colors

add a test with more than 256 colors in one frame

Merge pull request #35 from dloebl/local-max-table-trans

Fix: Transparency optimization could have been used for local tables with 256 entries