Embed element call (#3939)

* it works but only with the baseURL for now

* works but strings are not referenced properly

and we are using a dummy config.json which maybe is not required at all?

* test with EmbeddedElementCall repo

* updated the version

* ignore our own package

* updated version

removed using EC through the well known URL

* fix for remote URL overriding

* updated version

* fix for microphone and camera using local URL

* better solution

* Use version 0.9.0-release-test.3

* fix project

* removed workaround for emebedded EC url generation

* updated EC

* pr suggestions

* fix

* removed unnecessary configuration flag

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Co-authored-by: Hugh Nimmo-Smith <hughns@element.io>