X11 added to caveats DSL
X11 caveat DSL added to relevant casks
AppCast feed added to Xquartz cask
Merge pull request #4879 from radeksimko/xquartz-appcast

Add AppCast feed to Xquartz cask
encoding typo: `Encoding::ASCII_8BIT`

fixes #4876
Merge pull request #4881 from rolandwalker/encoding_typo

encoding typo: `Encoding::ASCII_8BIT`
cut v0.36.2
Merge pull request #4868 from radeksimko/x11-caveat

Add X11 support to the `caveats` mini-DSL