Update README instructions for `make doc-serve`.
Update README instructions for `make doc-serve`.

nathenharvey/habitat,rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,nathenharvey/habitat,rsertelon/habitat,georgemarshall/habitat,rsertelon/habitat,rsertelon/habitat,georgemarshall/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,nathenharvey/habitat,georgemarshall/habitat,habitat-sh/habitat,habitat-sh/habitat,georgemarshall/habitat,nathenharvey/habitat,georgemarshall/habitat,georgemarshall/habitat,habitat-sh/habitat,georgemarshall/habitat,habitat-sh/habitat,nathenharvey/habitat,habitat-sh/habitat,georgemarshall/habitat,rsertelon/habitat,nathenharvey/habitat