Document .WRITE/.READ/.EOF on IO::CatHandle
Document .WRITE/.READ/.EOF on IO::CatHandle

These just throw X::NYI; blocking out these methods from IO::Handle

SAP (Spec APpendices): https://github.com/perl6/roast/commit/e0f6f389d5
Rakudo impl: https://github.com/rakudo/rakudo/commit/9246b03520

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