Fix issue with commit 0482d521: styles.css now correctly imports into the online docs.

Fix an issue where a rogue </div> in Proof.md was causing display issues on the online docs.

doc/en/Authoring/Proof.md

@@ -182,14 +182,15 @@ Here is a proof of the great and wonderful theorem.
  <div class="proof-column">Lines don't need to have <code>proof-num</code> or <code>proof-block</code></div>
  <div class="proof-column">With further comments.</div>
 </div>
+
 <div class="proof-line">
  <div class="proof-column">The proof continues.</div>
  <div class="proof-column-2">With further comments.</div>
 </div>
+
 <div class="proof-line">
  <div class="proof-column">This concludes the proof.</div>
 </div>
-</div>
 
 It is possible to use `proof-column-2` style in the first column, but this looks odd and is not recommended.  The `proof-column-2` style is intended for only the second column.  The `proof-column` style is intended to be used in both columns.
 

mkdocs.yml

@@ -14,6 +14,7 @@ theme:
 docs_dir: 'doc'
 extra_css:
     - custom.css
+    - https://combinatronics.com/maths/moodle-qtype_stack/master/styles.css
 markdown_extensions:
     - mdx_math
     - extra