connection.session={} fixed. useCustomChromeExtensionForScreenCapturing added.

// if you deployed your own chrome extension on Google App
Store
connection.connection.useCustomChromeExtensionForScreenCapturing =
true;

`connection.session={}` fixed. If `session` is set to empty then
initiator will be `recvonly`:

https://github.com/muaz-khan/RTCMultiConnection-experimental#recent-changes