docs: Add a README.md file to explain the purpose of the directory.

Author: michael-berlin

docs/README.md

@@ -0,0 +1,6 @@
+If you're browsing this directory on GitHub, please ignore it.
+
+It contains the files which are serving www.vitess.io.
+
+If you're looking for documentation, you should find everything on www.vitess.io.
+

publish-site.sh

@@ -34,6 +34,9 @@ fi
 # Change to docs/ directory.
 pushd $website_dir >/dev/null
 
+# Restore README.md because it gets deleted by Jekyll.
+git checkout README.md
+
 # pre-commit checks
 set +e
 list=$(find . -name '*.html' ! -path '*/vendor/*' ! -path '*/web/*' | xargs grep -lE '^\s*([\-\*]|\d\.) ')