Added cross-ref to LRoutes in Routes documentation

Added a cross reference to LRoutes in the main Routes page so users will see relationship even if LRoutes doesn’t appear in the Sidebar.  Suggested by @silverailscolo - thanks!

help/en/html/tools/Routes.shtml

@@ -31,6 +31,13 @@
       <h1>JMRI: Routes Documentation</h1>
 
       <h2>What are Routes?</h2>
+
+      <p>[After reading this page, see also the <a href="LRoutes.shtml">LRoutes documentation</a>.
+      LRoutes offer extended routing capabilities, transparently implementing them as a series of 
+      <a href="Logix.shtml">Logix conditionals</a>. LRoutes are set up similarly to and are
+      capable of performing all of the tasks of Routes - and more. They can even trigger a Route 
+      for complete compatibility.]</p>
+
 
       <p>Routes are collections of Turnouts and/or Sensors whose
       states may be set all at once. Also when a Route is