Both a reason and rule ids are absent (e.g. a bare %% mermaid-lint-disable).
Reported as one diagnostic instead of both missing-reason and
empty-rules — see parseDirective.
The keyword only makes sense at the other scope: a -disable-file
written as a %% diagram comment (expected: 'file'), or a line/range/
diagram-scope keyword written as an <!-- --> HTML comment
(expected: 'body'). keyword is the full matched keyword, e.g.
mermaid-lint-disable-file.
A problem detected while parsing a directive.