go mod tidy

[blaggacao]

https://patch-diff.githubusercontent.com/raw/campoy/embedmd/pull/66.patch

Without specifically declaring the dependency, I got the following error in my build system (which does not assume anything).

go: inconsistent vendoring in /build/source:
        github.com/campoy/[email protected]: is marked as explicit in vendor/modules.txt, but not explicitly required in go.mod