Solutions available by adding ?answer=1 to sqlzoo.net URLs

[nicolas-raoul]

For instance https://sqlzoo.net/wiki/The_JOIN_operation?answer=1
This "cheat mode" does not work for all pages, though.

Please mention that in the README, some people might find it more convenient than going through SQL files (personally I prefer only checking on GitHub if I really can't find the solution by myself though).

Thanks! :-)