add a link from ! twigils to attributes.
add a link from ! twigils to attributes.

closes #967

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