Expose ways to add dash plugins and to configure dash playback.

[nweber]

Added information about additions to the README file.

[gkatsev]

Hi @nweber, thanks for the PR. We're trying to come up with a better way of passing options to source handlers. See videojs/video.js#2616
We probably won't pull this in until we resolve that (which, I think we're finally close to a consensus on what to do for it.

[forbesjo]

@gkatsev this change looks to be against the 1.x-dash.js-2.0.0 branch which is open against 1.x. 1.x is compatible with video.js 4.0 so it won't have access to any source handler enhancements.

[gkatsev]

Ah, missed that.

[gkatsev]

Is it still a tech then?

[gkatsev]

I guess it was still a source handler, I guess I forgot how early we got source handlers in videojs.

[gkatsev]

Also, the decisions we make for videojs/video.js#2616 may still be applicable to the older dash plugin.

[nweber]

Makes sense. I'm going to close this one for now. I've submitted a different pull request to enable a particular feature.