Index missing regex adverbs.
Index missing regex adverbs.

Fixes https://github.com/perl6/doc/issues/1046

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