comark/charts/unknown-column · Name only the table's columns in x and y

x and y name columns by their headers, exactly as the table writes them. A name the table doesn't have leaves the chart with nothing to draw, so the block shows the table alone. Separate several y columns with commas.

Incorrect

::chart{y="duck" title="Ducks per pond"}
| pond | ducks |
| --- | --: |
| north | 12 |
| south | 7 |
| east | 9 |
::

lint-comark example.mdexample.md:1:1 comark/charts/unknown-column::chart 1: y names column duck, but its table has pond and ducks.Separate several with commas, as in y="before, after".✖ 1 problem

Correct

::chart{y="ducks" title="Ducks per pond"}
| pond | ducks |
| --- | --: |
| north | 12 |
| south | 7 |
| east | 9 |
::

lint-comark example.md✔ No problems