the example event id had 21 leading zeroes, not 20
I provided new C code that has been tested to work (I couldn't get the original example code to work) and I provided some JavaScript code to test event ids as well.
I did not re-compute the event id for the example event; I simply changed the nonce to be 21. Since it is an example, it may not matter that the event id is not correct.
Thanks-to: Cameri and scsibug for the initial idea of using the id for PoW
Thanks-to: David A. Harding for the difficulty commitment idea
Signed-off-by: William Casarin <jb55@jb55.com>