DOC: config: add example for server "track" keyword

As requested on GH #2325, "track" server keyword could benefit from a
simple config example to show how to make use of it.

That's what we're doing in this commit, thanks to GH user @HAkmiller
for the suggestion.

diff --git a/doc/configuration.txt b/doc/configuration.txt
index b79b028c99e2f1a9548f5417cb28024e2335f85c..bfe744f87bb2406050becacc3b383d86bc5bfd21 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -18997,6 +18997,15 @@ track [<backend>/]<server>
   enabled. If <backend> is omitted the current one is used. If disable-on-404 is
   used, it has to be enabled on both proxies.
 
+  Example :
+
+    backend A
+    server a1 1.1.1.1:80 track B/b1
+    server a2 1.1.1.2:80 track B/b1
+
+    backend B
+    server b1 2.2.2.2:80 check
+
 tls-tickets
   May be used in the following contexts: tcp, http, log, peers, ring