Can go-astisub parse HDMV/PGS subtitle?

[tony9527167]

see also https://gist.github.com/daniel-j/2da75add26f548e57aae85d6471667dd

[asticode]

Right now it can't, but that could be a good addition. However I didn't find any specification online.

Also I won't have time to work on this anytime soon, but as usual I'm welcoming PRs