comark/annotate/missing-src · Give every ::screenshot a src

A ::screenshot without src has no image, so its marks and notes point at nothing.

Incorrect

::screenshot{alt="The pond map with three ducks"}
::

lint-comark example.mdexample.md:1:1 comark/annotate/missing-srcscreenshot 1 ("The pond map with three ducks"): src is required.Point it at the image file.✖ 1 problem

Correct

::screenshot{src="/pond.png" alt="The pond map with three ducks"}
::

lint-comark example.md✔ No problems