Merge pull request imgbot#681 from dabutvin/dependabot/nuget/MSTest.T…

…estFramework-2.1.2

Bump MSTest.TestFramework from 2.1.1 to 2.1.2

Merge pull request imgbot#654 from dabutvin/gifsicle

add gifsicle compression

Merge pull request imgbot#624 from dabutvin/threshold

configuration option for compression threshold (fixes #562)

update path to libgit binary

Merge pull request imgbot#507 from dabutvin/update-docs-with-wiki-sup…

…port

Updated docs regarding wiki compression

mention the new external settings in the configuration doc

downgrade to ubuntu-16.04

update to elgohr/Publish-Docker-Github-Action@2.6

Merge pull request imgbot#495 from ElSiipo/master

add support for mozJpeg compression

Merge pull request imgbot#489 from dabutvin/check-size

make sure fileAfter size is greater than 0 before adding