add readme

Author: lucarin91

README.md

@@ -0,0 +1,19 @@
+# Arduino Flasher CLI
+
+A tool to download and flash Debian images on the board.
+
+## Docs
+
+For a full guide on how to use it, see the [User documentation](https://docs.arduino.cc/tutorials/uno-q/update-image/).
+
+## Build and test it locally
+
+Build it with `task build` and run:
+
+```sh
+# Flash the latest release of the Debian image
+./build/arduino-flasher-cli flash latest
+
+# Flash a local image. It works with either an archived or extracted image
+./build/arduino-flasher-cli flash path/to/downloaded/image
+```