Added Lua section to the user manual

test/page.lp

@@ -2,6 +2,7 @@
   -- Lua server pages have full control over the output, including HTTP
   -- headers they send to the client. Send HTTP headers:
   print('HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n')
+
 ?><html><body>
 
 <p>This is an example Lua server page served by
@@ -10,6 +11,14 @@ Mongoose has Lua, Sqlite, and other functionality built in the binary.
 This example page stores the request in the Sqlite database, and shows
 all requests done previously.</p>
 
+  <p> Today is <? print(os.date("%A")) ?>
+  <p> HTTP headers: <br>
+   <?
+     for name, value in pairs(request_info.http_headers) do
+       print(name, ' : ', value, '<br>')
+     end
+   ?>
+
 <pre>
 <?
   -- Open database