x/pkgsite: show `cmd/go` as the top entry in search result for 'go'

[hyangah]

What is the URL of the page with the issue?

https://pkg.go.dev/search?q=go

Screenshot

What did you do?

search go

What did you expect to see?

go command doc (https://pkg.go.dev/cmd/go)

What did you see instead?

It's a command, so it's unlikely to see the page highly ranked in the current pkg site.
But I think go is special and may deserve special care.

Users can access the page with cmd/go query.