Support -- as a comment delimiter for directives

Currently only [html-validate-disable-next my-rule: comment] is supported but since eslint uses -- for the same purpose it would be nice to support both.

mentioned in commit 7c90250c

mentioned in merge request !648 (merged)

mentioned in commit 34cc70c0

closed with commit 7c90250c

closed with merge request !648 (merged)

mentioned in commit 12ab38ba