Add support for two element kinds that currently fall through to the unknown content element error.
-
math.cancel— maps to MathML<menclose>with a strike notation.inverted: trueflips the slash direction;cross: truecombines both diagonals. -
bare
scripts(x)/limits(x)— these wrappers only steer sub/superscript placement in the enclosing operator (handled in_has-limits). When they appear standalone without any attached scripts they're a no-op — unwrap and recurse into the body.
A note on <menclose>
MathML Core marks <menclose> as deprecated, but Chromium / Firefox / WebKit all still render it, and there's no Core replacement yet.