Add support for math tables

[cbreeden]

I need to be able to parse relevant information from the MATH table. I have started some scratch work to get things going. My question is: would you be interested in supporting parsing the MATH table and other math related information from an opentype font?

Now that I've started with some scratch work, I feel like I understand your code base better (one of those, you don't understand what's going on until you try it yourself kind of things) and would be interested in doing the required coding if you wouldn't mind me asking a few questions along the way.

[IvanUkhov]

Thanks for reaching out! In general, the intention with this and related crates is to cover the entire standard. So yes, I’m very much interested in supporting the MATH table! And yes, I’ll be happy to answer any questions. Please note that I’ve started updating the crate with respect to the 1.8 release of OpenType; see branch opentype-1.8 and pull request #4. Thanks again!