[foms] WebVTT implementation in browsers

[Thomas Levine]

Dear Silvia,

Thank you for the information that audio without video will be no
trouble.

What data are you thinking of for test material, and how should
I provide them in order that they be useful as standardised test
material? Or, perhaps this could be a project for FOMS.

Regarding the languages of tracks, can you explain why IETF language
tags are the way they are, why there is a srclang attribute, and why
it is required rather than optional? I presented the situation of two
languages for caption file as one example of how the HTML/WebVTT model
of language classification does not match my language classification.
I have extended that section to clarify.

Academic salutations,
Thomas