be-tarask language subtag registration form

[Frank Ellermann]

Yury Tarasievich wrote:

> I don't know what would be made of it by the tag makers.

Syntactically and procedurally the request is for a variant
"tarask" with prefix "be".  This will (syntactically) allow
tags like be-tarask, be-Cyrl-tarask, be-Latn-tarask, and
be-Brai-AQ-tarask among others.

JFTR, because C.E. asked about the variant being bound to
be-Cyrl somehow.  For that effect listing two prefixes "be"
and "be-Cyrl" could be clearer - there's no direct way to
say that a tag be-Latn-tarsk would be dubious in the subtag
registry, unless it's in a comment.

Frank