Add missing QHelp files

javascript/ql/src/Metrics/FLinesOfCodeOverview.qhelp

@@ -0,0 +1,32 @@
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+<fragment>
+<p>
+There are a number of problems associated with a high number of lines of code:
+</p>
+
+<ul>
+<li>
+It can be difficult to understand and maintain, even with good tool support.
+</li>
+
+<li>
+It increases the likelihood of multiple developers needing to work on the same
+file at once, and it therefore increases the likelihood of merge conflicts.
+</li>
+
+<li>
+It may increase network traffic if you use a version control system that requires the whole file to
+be transmitted even for a tiny change.
+</li>
+
+<li>
+It may arise as a result of bundling many unrelated things into the
+same file, and so it can indicate weak code organization.
+</li>
+</ul>
+
+</fragment>
+</qhelp>