[io grant] Finish up IO::Path.dir docs
[io grant] Finish up IO::Path.dir docs

- Fix up formatting
- Mention `test` tests against Str names, not IO::Paths
- Use proper $*HOME instead of env var and don't stringify IO::Paths

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