Migrate from internal hosting to GitHub pages

* Add Twitter card customizations that have been kept in
an internal fork
* Add CNAME needed for GitHub pages

docs/CNAME

@@ -0,0 +1 @@
+typhoon.psdn.io

mkdocs.yml

@@ -6,6 +6,7 @@ repo_name: poseidon/typhoon
 repo_url: https://github.com/poseidon/typhoon
 theme:
   name: material
+  custom_dir: 'theme'
   features:
     - navigation.tabs
     - navigation.instant

theme/main.html

@@ -0,0 +1,10 @@
+{% extends "base.html" %}
+
+{% block extrahead %}
+  <meta name="twitter:card" content="summary_large_image">
+  <meta name="twitter:site" content="@typhoon8s">
+  <meta name="twitter:creator" content="@dghubble">
+  <meta name="twitter:title" content="Minimal and free Kubernetes clusters">
+  <meta name="twitter:description" content="Kubernetes clusters for AWS, Azure, bare-metal, Google Cloud, and DigitalOcean">
+  <meta name="twitter:image" content="https://storage.googleapis.com/poseidon/typhoon-twitter-card.png">
+{% endblock %}