Add remote video overlay

Fix remote audio not working when viewing another conversation.
Add a remote video overlay when in a call, but viewing a different page.

New components:
- VideoOverlay
- RemoteVideoOverlay: Video overlay for the remote stream when in a
  different page. Clicking it will redirect to the current call page.
- VideoStream: renders a video from a MediaStream and can
  output audio to the device with id `audioOutDeviceId`

Misc changes:
- Can click local video to make bigger

Change-Id: If1bb0b10c137944c405d540f041ebfe8005f9251
diff --git a/client/src/components/Button.tsx b/client/src/components/Button.tsx
index 4e0d5ac..ddd99e9 100644
--- a/client/src/components/Button.tsx
+++ b/client/src/components/Button.tsx
@@ -34,7 +34,7 @@
 } from '@mui/material';
 import { styled } from '@mui/material/styles';
 import EmojiPicker, { IEmojiData } from 'emoji-picker-react';
-import React, { ComponentType, MouseEvent, ReactNode, useCallback, useState } from 'react';
+import { ComponentType, MouseEvent, ReactNode, useCallback, useState } from 'react';
 
 import {
   Arrow2Icon,