[clang-doc] generate comments for functions

Change the function partial to enable comments to be generated for
functions. This only enables the brief comments in the basic project.

Author: evelez7

clang-tools-extra/clang-doc/assets/function-template.mustache

@@ -14,10 +14,10 @@
             </code>
         </pre>
         {{! Function Comments }}
-        {{#FunctionComments}}
+        {{#Description}}
         <div>
             {{>Comments}}
         </div>
-        {{/FunctionComments}}
+        {{/Description}}
     </div>
 </div>