Consider adding seekable() method

[nickygerritsen]

Dash.js supports a metric called DVRInfo, which should give us enough information to use for a seekable() implementation for DVR live content. See also https://github.com/Dash-Industry-Forum/dash.js/issues/1384 for some info.

I am willing to add the seekable() implementation myself, as it seems not too hard (as soon as we know what to do with the fact that DVRInfo is an array).

As far as I know just adding a seekable() method to the Html5DashJS class should do the trick, right?

Any objections or opinions?

[nickygerritsen]

Btw I do like to wait for at least #60 before working on this :)

[nickygerritsen]

We can even use the event data, which seems better than the DVRInfo array :)

[forbesjo]

Adding to backlog