docs: render 'MyFirstObjectWalk'
docs: render 'MyFirstObjectWalk'

Since this tutorial is already formatted in Asciidoc,
add it to the list of documents that are rendered on the website.

git/git-scm.com,git/git-scm.com,git/git-scm.com,Mokolea/git-scm.com,Mokolea/git-scm.com,mosoft521/gitscm-next,mosoft521/gitscm-next,Mokolea/git-scm.com,mosoft521/gitscm-next,mosoft521/gitscm-next,Mokolea/git-scm.com,git/git-scm.com