Add example for SetHash initialization.
Add example for SetHash initialization.

See issue #1939

stmuk/doc,jonathanstowe/doc,perl6/doc,stmuk/doc,tbrowder/doc,MasterDuke17/doc,jonathanstowe/doc,perl6/doc,perl6/doc,tbrowder/doc,stmuk/doc,MasterDuke17/doc,jonathanstowe/doc,dmaestro/doc,perl6/doc,stmuk/doc,dmaestro/doc,dmaestro/doc,MasterDuke17/doc,stmuk/doc,perl6/doc,jonathanstowe/doc,tbrowder/doc,jonathanstowe/doc,MasterDuke17/doc,dmaestro/doc,dmaestro/doc,tbrowder/doc