[ep-matrix] Customize the Matrix dimension server to allow use of microphone and camera in generic widgets

[malemburg]

The dimensions integration manager we use is this one: https://github.com/turt2live/matrix-dimension

Here's the template we'd need to change: https://github.com/turt2live/matrix-dimension/blob/master/web/app/widget-wrappers/generic/generic.component.html

and this is an example of how it should look like:
https://github.com/turt2live/matrix-dimension/blob/master/web/app/widget-wrappers/bigbluebutton/bigbluebutton.component.html

In our fork, the link of the template is: https://github.com/europython/matrix-dimension/blob/ep2021/web/app/widget-wrappers/generic/generic.component.html

[malemburg]

With this change we may be able to get the Wonder.me integration working after all, since they seem to have fixed some things on their side, which seems to make embedding work again.