scrcpy v1.4

Changes since v1.3:
 - Send raw key events for letters to use keyboard in games (#87)
 - Add feature to push file to /sdcard/ via drag & drop (#226)
 - Add command-line option to start in fullscreen (#252)
 - Improve error message on missing adb (#236, #254)
 - Keep the console open on error on Windows (#261)
 - Fix possible session crash on close (#52, #182)
 - Return non-zero value on connection loss (#204)
 - Avoid additional buffer copy in userspace on the server
 - Update platform-tools to 28.0.1 (adb) included in Windows releases
   (#224)
 - Update FFmpeg to 4.0.2 included in Windows releases