Add esputil flash command

[sellicott]

I was trying to reflash the firmware on my esp32s2-funprog, but I can't figure out the invocation to use esputil to replace the esptool.py command. That should probably get added to the readme (https://github.com/cnlohr/esp32s2-cookbook)

[cnlohr]

Sorry just seeing this now. I don't understand this comment.

[sellicott]

In the documentation page for the esp32-s2 programmer there is a documented command to reflash the firmware using esptool.py (https://github.com/cnlohr/esp32s2-cookbook/tree/master/ch32v003programmer). It would be nice if there was documentation to use esputil to flash the programmer since it is mentioned directly as a superior alternative in the readme.

[cnlohr]

Oh you should be able to just bang that together, no?

[cnlohr]

If you do I'd gladly add it to the page!