DOC: lua: Proxy class doc update

Following the patch adding the name of the proxy, this patch contains
the associated doc update.
diff --git a/doc/lua-api/index.rst b/doc/lua-api/index.rst
index 113aad6..541d960 100644
--- a/doc/lua-api/index.rst
+++ b/doc/lua-api/index.rst
@@ -785,6 +785,10 @@
   This class provides a way for manipulating proxy and retrieving information
   like statistics.
 
+.. js:attribute:: Proxy.name
+
+  Contain the name of the proxy.
+
 .. js:attribute:: Proxy.servers
 
   Contain an array with the attached servers. Each server entry is an object of