DOC: lua: add sticktable class reference from Proxy.stktable

Add a reference hint for the sticktable class and mention it from
Proxy.stktable documentation to allow easy navigation from a web
browser.

(cherry picked from commit 034461fd73634410d58f0225388a9e49e9636fb2)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit e5ad347df3eadb4bcb7bdd1bb76e3658deda425a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit e793a4ff5a0ed8d70747857d7352251083a8192d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit ffd9292d7a397535e3c90e68ad31fee633fdf66e)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/doc/lua-api/index.rst b/doc/lua-api/index.rst
index 44432e3..7cec644 100644
--- a/doc/lua-api/index.rst
+++ b/doc/lua-api/index.rst
@@ -868,7 +868,8 @@
 
 .. js:attribute:: Proxy.stktable
 
-  Contains a stick table object attached to the proxy.
+  Contains a stick table object of type :ref:`sticktable_class` attached to the
+  proxy.
 
 .. js:attribute:: Proxy.listeners
 
@@ -2693,6 +2694,8 @@
   :see: :js:func:`AppletTCP.unset_var`
   :see: :js:func:`AppletTCP.set_var`
 
+.. _sticktable_class:
+
 StickTable class
 ================