message: add mention to usbboot devices support
  Change-type: patch
  Changelog-entry: Add mention to usbboot compatibility
diff: Etcher is a powerful OS image flasher built with web technologies to ensure
  flashing an SDCard or USB drive is a pleasant and safe experience. It protects
  you from accidentally writing to your hard-drives, ensures every byte of data
  -was written correctly and much more.
  +was written correctly and much more. It can also flash directly Raspberry Pi devices that support the usbboot protocol
  [![Current Release](https://img.shields.io/github/release/balena-io/etcher.svg?style=flat-square)](https://balena.io/etcher)
  ![License](https://img.shields.io/github/license/balena-io/etcher.svg?style=flat-square)
  