Add a navigation article to the documentation for better sign-posting off relevant sections.

Because of the theme used (to look like a blog post) the documentation has no clear navigation. This new document helps rectify that without changing the whole theme.

Signed-off-by: David Jackson <58445547+daj-code@users.noreply.github.com>

Author: daj-code

docs/content/intro/navigation.md

@@ -0,0 +1,13 @@
+---
+title: "Navigation"
+date: 2020-12-21T20:26:44+00:00
+draft: false
+# Give heavy weight so that it appears at the top of the documentation homepage
+weight: 100
+---
+
+For installation, and basic usage, see [getting started]({{< ref "/documentation/getting-started.md" >}} "floki: Getting Started").
+
+For an overview of the features of `floki`, see the [feature overview]({{< ref "/intro/feature-overview.md" >}} "floki: Feature Overview").
+
+Full documentation can be found [here]({{< ref "/" >}} "floki: Documentation").