DFU make rule, update Readme (#650)

Co-authored-by: あく <alleteam@gmail.com>

docker-compose.yml

@@ -1,16 +1,12 @@
 version: '3'
 services:
   dev:
-    build: docker
-    network_mode: "host"
+    image: flipperdevices/flipperzero-toolchain
+    network_mode: host
     privileged: true
     tty: true
     stdin_open: true
     volumes:
       - .:/project
       - /dev/bus/usb:/dev/bus/usb
-    working_dir: "/project"
-    environment:
-      DISPLAY: $DISPLAY
-      TERM: xterm-256color
-      PATH: /root/.cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+    working_dir: '/project'