Comment on non-Sparkle appcast

See Issue #5057
Add ForkLift version 2.6.1
Update to Dogecoin-Qt 1.7
Merge pull request #5075 from hanxue/epubtopdf-appcast

Comment on non-Sparkle appcast
Merge pull request #5079 from Fapper/patch-1

Update to Dogecoin-Qt 1.7
Merge pull request #5077 from vinkla/forklift

Add ForkLift version 2.6.1
MacDown 0.1

New cask MacDown, version 0.1 - with appcast xml