`.toBeSortedBy(columnName, order)` mathcher

[SevenOutman]

Describe the feature you'd like:

Assert that an ARIA table is currently sorted by a certain column in certain order.

Suggested implementation:

Check that an ARIA columnheader with corresponding name is present in the table, and it's got the aria-sort attribute with correct value.

[tsturtz]

+1

[konrazem]

+1