Move gh-pages branch files into /docs and add test files

- Jekyll ignore `/docs` and `/test` folders when using from root
- Update Staticman config to point to correct branch and data file location
- Replace `{{ base_path }}` references with `absolute_url` filter
- Update documentation

docs/_layouts/home.html

@@ -0,0 +1,13 @@
+---
+layout: archive
+---
+
+{% include base_path %}
+
+<h3 class="archive__subtitle">{{ site.data.ui-text[site.locale].recent_posts | default: "Recent Posts" }}</h3>
+
+{% for post in paginator.posts %}
+  {% include archive-single.html %}
+{% endfor %}
+
+{% include paginator.html %}