Command-line options for AllAboutMonstrs entry

As usual we added command-line options to our, but in this case I forgot to mention them in the README

On Linux you can toggle full-screen with F11.  If you are on Windows or OSX I think you need to run: --full
to get full screen. Otherwise it's 1024x768 which on most monitors these days isn't all that big.
I remember when 800x600 carried a risk of eliminating half your potential user base, but I digress...

./ --help lists the other options.