Dangerfile: warn about absent link to an original issue.

Author: php-coder

Dangerfile

@@ -670,6 +670,13 @@ else
 	end
 end
 
+if github.pr_body !~ /Addressed to #\d+/
+	warn(
+		"danger check: pull request description doesn't contain a link to original issue.\n"\
+		"Consider adding a comment in the following format: `Addressed to #XXX` where `XXX` is an issue number"
+	)
+end
+
 commits = git.commits.size
 if commits > 1
 	if git.commits.any? { |c| c.message =~ /^Merge branch/ || c.message =~ /^Merge remote-tracking branch/ }