We support these setting these as attributes on the `<table>` element
itself, so I suppose it also makes sense to support their DOM APIs as
well. This trades a teensy bit of code for compatability with a some old
web content.
Testing: This causes a handful of reflection subtests to start passing.
There
isn't much testing for the behavior of the attributes, but this is
legacy
behavior so it sort of makes sense.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>