fix: include wget in the list of packages to install on macOS
A follow-up to needed now that has landed.  macOS does not include
wget in the base install.
@@ -34,7 +34,7 @@ rest of these instructions assume you have it.
To install most of the [external dependencies][ext], run
{% highlight bash %}
-for pkg in asciidoc cmake go graphviz node parallel source-highlight ; do
+for pkg in asciidoc cmake go graphviz node parallel source-highlight wget ; do
brew install $pkg
done
