fix(external_api): Pass Feature-Policy display-capture to the iframe
fix(external_api): Pass Feature-Policy display-capture to the iframe

Starting from version 74, firefox need to be explicitly allowed to capture the screen from an iframe for screensharing. This new Feature-Policy is called "display-capture".
See: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Feature-Policy/display-capture
jitsi/jitsi-meet,gpolitis/jitsi-meet,bgrozev/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,bgrozev/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,bgrozev/jitsi-meet,jitsi/jitsi-meet,jitsi/jitsi-meet,jitsi/jitsi-meet,bgrozev/jitsi-meet,bgrozev/jitsi-meet,gpolitis/jitsi-meet,bgrozev/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet