Add to check for ending punctuation

[NSoiffer]

There is currently a check to avoid speaking punctuation at the end of a math expression.

This Wikipedia page has a . followed by a <mspace width='thinmathspace'/> and that is not being caught.

Make canonicalization throw out spaces at the start/end (if in math/mrow).

[NSoiffer]

Note: there is a test for this called ignore_period_and_space. It is currently has #[ignore].