Update README.md

Add note for SKR STM32 boards.

README.md

@@ -34,7 +34,10 @@ The plugn supports a variety of boards, based on the MCU (processor) they have:
 * 'AT90USB' family 8-bit MCUs (Printrboard)
 * 'LPC1768' MCUs (MKS SBASE, SKR v1.1 and v1.3, etc.)
 * 'SAM' family 32-bit MCUs (Arduino DUE, etc.)
-* 'STM32' family 32-bits MCUs with embedded ST serial bootloader (FYSETC CHEETAH)
+* 'STM32' family 32-bits MCUs with embedded ST serial bootloader (FYSETC Cheetah, **not** SKR Pro)
+
+#### Special Note for SKR STM32 Boards
+It seems that SKR have included a custom bootloader which enables their STM32-based boards (SKR Pro v1.1 and SKR Mini E3) to be flashed using the same copy-and-reset procedure as their LPC1768-based boards.  **Please follow the LPC1768 instructions for SKR STM32 boards.**
 
 Please open a [Github issue](https://github.com/OctoPrint/OctoPrint-FirmwareUpdater/issues) if you would like a new board or MCU to be supported. If it's a new type of board which requires hardware testing please consider making a [donation](#Donations) to help fund the costs.
 
@@ -54,6 +57,9 @@ The appropriate flashing tool for the board type needs to be selected.
 | SAM          | bossac         |
 | STM32        | stm32flash     |
 
+#### Special Note for SKR STM32 Boards
+It seems that SKR have included a custom bootloader which enables their STM32-based boards (SKR Pro v1.1 and SKR Mini E3) to be flashed using the same copy-and-reset procedure as their LPC1768-based boards.  **Please follow the LPC1768 instructions for SKR STM32 boards.**
+
 Plugin settings vary depending on the flashing tool and are documented below.
 
 ## Board-Specific Configuration