Revive Nanoc support

[ennru]

#203 moved the Nanoc support into a separate module but didn't make it part of the build.

[satabin]

Hi @ennru,

we are using nanoc to generate our fs2-data website and cannot upgrade due to the lacking module. My understanding is that only the sbt project is missing in build.sbt as the code seems to be there already. Is re-enabling nanoc support only about adding an sbt module or is there more to it?

[ennru]

That might be all that is needed to revive it. Please try it out locally and suggest the required changes in a PR.