Add support for Video Texture Target

[vincentfretin]

Add a video-texture-target component. I have a modified networked-video-source that supports using it on a media-frame 2d I'm using with janus adapter. I need to verify if it would be working properly with easyrtc adapter.

[vincentfretin]

I also created this issue c-frame/sponsorship#2 some times ago, so probably do a fix in networked-aframe repo as well.

My modified networked-video-source is dependent on a naf:reconnecting event for naf-janus-adapter I didn't contributed yet, and also on a video system that may be specific to janus adapter. I need to figure out how to use it with the easyrtc adapter and also contribute a share screen or share camera button like I did for MicButton.

[vincentfretin]

I added my video-texture-target component. But there is still a lot of code to contribute probably in a different repository to properly use it for screen sharing.

[vincentfretin]

I pushed my code working with janus adapter in networked-aframe/naf-valid-avatars#34
Still need some changes to be used with easyrtc adapter.