Add categories to FAQ

This TOC is the kramdown version, so the levels are defined site-wide.

_config.yml

@@ -82,7 +82,7 @@ kramdown:
   auto_ids: true
   footnote_nr: 1
   entity_output: as_char
-  toc_levels: 1..6
+  toc_levels: 1..2
   smart_quotes: lsquo,rsquo,ldquo,rdquo
   enable_coderay: false
 

_docs/110_faq.md

@@ -1,8 +1,10 @@
 ---
 title: "Frequently Asked Questions"
 permalink: /docs/faq
-#{% include toc title="Questions" %}
+# TOC levels is dictated by toc_levels in _config.yml
+# Update to front-matter TOC after upgrading MMistakes
 ---
+{% include toc title="Categories" %}
 
 ## Usage