Add missing QHelp files

javascript/ql/src/Comments/CommentedOutCodeQuery.qhelp

@@ -0,0 +1,25 @@
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+
+<overview>
+<p>
+Commented-out code is distracting and confusing for developers who read the surrounding code,
+and its significance is often unclear. It will not get compiled or tested when the code around
+it changes, so it's likely to break over time. For these reasons, commented-out code should be
+avoided.
+</p>
+
+</overview>
+
+<recommendation>
+
+<p>
+Remove or reinstate the commented-out code. If you want to include a snippet of example code
+in a comment, consider enclosing it in quotes or marking it up as appropriate for the source
+language.
+</p>
+
+</recommendation>
+</qhelp>