Introduction to MNX-Common

Hi all,

I've just published a short "Introduction to MNX-Common," which outlines
our high-level goals for the MNX-Common format. You can find it on this
page:

    https://github.com/w3c/mnx

Of course, we've already had a draft specification for a while — but I
thought we'd benefit from a light introduction written in a less formal
way. As I'm a new co-chair tasked with leading MNX development, this was
also a useful exercise that helped crystallize my own thoughts.

Those of you who have been following MNX's development won't find much new
in this short document, but I hope the additional context is useful to the
community.

Cheers,
Adrian