this commit adds support for the `::add-mask::` command, which was implemented as a stub before. it does not cover debug output that appears when you run act in verbose mode Co-authored-by: Björn Brauer <bjoern.brauer@new-work.se> Co-authored-by: Markus Wolf <markus.wolf@new-work.se> Co-authored-by: Björn Brauer <bjoern.brauer@new-work.se> Co-authored-by: Markus Wolf <markus.wolf@new-work.se>