For the most part the changes are taking the "static propTypes" declaration off
of components and declaring them as Flow types. Sometimes to support flow some
method signatures had to be added. There are some exceptions in which more had
to be done to tame the beast:
- AbstractVideoTrack: put in additional truthy checks for videoTrack.
- Video: add truthy checks for the _videoElement ref.
- shouldRenderVideoTrack function: Some component could pass null for the
  videoTrack argument and Flow wanted that called out explicitly.
- DisplayName: Add a truthy check for the input ref before acting on it.
- NumbersList: Move array checks inline for Flow to comprehend array methods
  could be called. Add type checks in the Object.entries loop as the value is
  assumed to be a mixed type by Flow.
- AbstractToolbarButton: add additional truthy check for passed in type.

* feat(welcome-page): Redesign.

* Style adjustments.

It doesn't seem to work properly.

That is only required if we'd want our backend to authenticate on behalf of our
users. If the app is to authenticate directly it's not needed.

It was moved to js-utils, so make use of it.

* Removed unnecessary string wrapping

This involves redesign of the web recording dialog in order to look the
same as the mobile one.

- Change "features/chat" to support listening for new chat messages
  and storing them, removing that logic from conference.js.
- Combine chat.scss and side_toolbar_container.css, and remove unused
  scss files. Chat is the only side panel so the two concepts have
  been merged.
- Remove direct access to the chat feature from non-react and non-redux
  flows.
- Modify the i18n translate function to take in an options object.
  By default the option "wait" is set to true, but that causes
  components to mount after the parent has been notified of
  an update, which means autoscrolling down to the latest rendered
  messages does not work. With "wait" set to false, the children
  will mount and then the parent will trigger componentDidUpdate.
- Create react components for chat. Chat is the side panel
  plus the entiren chat feature. ChatInput is a child of Chat and
  is used for composing messages. ChatMessage displays one message
  and extends PureComponent to limit re-renders.
- Fix a bug where the toolbar was not showing automatically when
  chat is closed and a new message is received.
- Import react-transition-group to time the animation of the
  side panel showing/hiding and unmounting the Chat component.
  This gets around the issue of having to control autofocus if the
  component were always mounted and visibility toggled, but
  introduces not being able to store previous scroll state
  (without additional work or re-work).

* feat: Displays the server region in the stats panels.

* feat: Displays the server count in the local stats panel.

* ref: Renames a variable.

* fix: Makes bridgeCount a number, clarifies docs.

* chore: Updates lib-jitsi-meet to 1ac6df97e3.

There are (at least) two changes that are breaking:
- defaultTab is gone
- The re-rendering logic looks to have been re-written so that
  passing in a new array of tabs causes a re-render, which can
  reset the currently selected tab.

The fixes involved removing defaultTab from each tab configuration,
as it is no longer respected anyway. Also, instead of letting Tabs
be uncontrolled and allowing it to set its own selected, which
would result in the first tab automatically being selected on
Tabs re-render, use Tabs a controlled prop to dicate which
tab is selected; this is accomplished by specifying a selected
prop.