add support for the IAMF audio codec

[robUx4]

As Alliance for Open Media seems to only care about promoting the non-free ISOBMFF, we'll have to the mapping ourselves.

The ISOBMFF mapping is described in https://aomediacodec.github.io/iamf/v1.1.0.html.

It seems to be a codec wrapping other codecs.

[shmerl]

Having matroska handling IAMF would be nice.