[x/tour] content: reinstate instructions for running locally
[x/tour] content: reinstate instructions for running locally

This was lost in the conversion from HTML to present format in
6cf2ff.

Fixes golang/go#12134

Change-Id: I58a16ceb4a5edfbccb9733c3df2d409022bb6ffa
Reviewed-on: https://go-review.googlesource.com/15652
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>
X-Tour-Commit: bf1c16d1d675bc6c186f3fd636923da795f7b603

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website