Update FWUPDATE.md

Added section on manually fetching and verifying the hash, including where to find the published hashes for Jade and Jade Plus firmware and the differences between the cmphash and fwhash. Also corrected the original typo (from "is desired" to "if desired").

Author: tokyovyse

FWUPDATE.md

@@ -38,13 +38,21 @@ As above - run the script and select the firmware to fetch.
 ./update_jade_fw.py
 ```
 
-When asked whether to save a local copy of the firmware file, answer 'y' - a copy of the firmware will be written to the current directory.  A .hash file containing the hex hash of the final firmware may also be written.
+When asked whether to save a local copy of the firmware file, answer 'y' - a copy of the firmware will be written to the current directory with a `.bin` file extension.  A `.hash` file containing the hex hash of the final firmware will also be written.
 
-When asked whether to upload this file to the connected Jade unit - answer 'n' - the script should exit.
+When asked whether to upload this file to the connected Jade unit - answer 'n' - the script will then exit.
 
-The sha256 hash of the file can then be checked, and if desired the downloaded file can be verified against the source code in this repo (given the appropriate tag/config) - see REPRODUCIBLE.md.
+The sha256 hash of the .bin file can then be checked against the **cmphash** (compressed hash) provided by Blockstream for the relevant firmware version. This is provided in the firmware metadata JSON file for each device type which can be found here:
 
-NOTE: if a .hash file is also written, this contains the hash of the final uncompressed firmware - in the case of a delta this hash refers to the complete firmware image obtained by applying the delta to the firmware currently running in the Jade unit.
+| Jade Hardware Type          | URL                                                       |
+| --------------------------- | ----------------------------------------------------------|
+| Jade 1.0 (true wheel)       | https://jadefw.blockstream.com/bin/jade/index.json        |
+| Jade 1.1 (rocker/jog-wheel) | https://jadefw.blockstream.com/bin/jade1.1/index.json     |
+| Jade 2.0 (two buttons)      | https://jadefw.blockstream.com/bin/jade2.0/index.json     |
+
+If desired, the downloaded file can also be verified against the source code in this repo (given the appropriate tag/config) - see REPRODUCIBLE.md.
+
+NOTE: The `.hash` file contains the hash of the final uncompressed firmware - in the case of a firmware delta this hash refers to the complete firmware image obtained by applying the delta to the firmware currently running in the Jade unit. This hash can be checked against the **fwhash** given in the same links above, and this is the hash that will be displayed on the screen of the Jade unit at the next step.
 
 This local file can then be uploaded to the Jade hardware as follows:
 ```