* Fix placement of new messages separator
* Ignore your own posts when determining start of new messages
* Cache lastViewedAt in ChannelPostList until switching channels
* Increase padding around DateHeader & NewMessagesDivider
* Improve styling of new messages divider line
* Use async await for ChannelDrawerList.onSelectChannel
* Convert DateHeader to functional component
* Indicate start of new messages in posts list
* Use flag prop to indicate start of new messages in posts list
* Declare style props with View.propTypes.style