Added some advice to failed verify output for debugging help.

This is a lovely little teaching/learning tool, but it took me quite a few failed attempts to verify with syntax errors before I realised I could do `stream-adventure run` as well as `stream-adventure verify` to be able to debug my attempts (I know... RTFM).

Adding a little bit of advice to the failed verification message might just help reduce the frustration levels of people who plough through without reading the help.