Turns out React Native's timers (setTimeout / setInterval) don't run while the
app is in the background: https://github.com/facebook/react-native/issues/167

This patch replaces the global timer functions with those from the
react-native-background-timer package, which work in the background.

These timers won't magically make an application work in the background, but
they will run if an application already happens to run in the background. That's
our case while in a conference, so these timers will run, allowing XMPP pings to
be sent and the conference to stay up as long as the user desires.

Until we make a decision on access modifier hints and adopt a respective
coding style, consistency is king.

React Native provides Platform.

jitsi/lib-jitsi-meet#66b601e disabled the execution of Temasys'
adapter.screenshare.js on browsers on which we don't use Temasys such as
React Native. Henceforth, no Temasys workarounds are necessary on React
Native.

As an intermediate step on the path to merging jitsi-meet and
jitsi-meet-react, import the whole source code of jitsi-meet-react as it
stands at
2f23d98424
i.e. the lastest master at the time of this import. No modifications are
applied to the imported source code in order to preserve a complete
snapshot of it in the repository of jitsi-meet and, thus, facilitate
comparison later on. Consequently, the source code of jitsi-meet and/or
jitsi-meet-react may not work. For example, jitsi-meet's jshint may be
unable to parse jitsi-meet-react's source code.