DOC: management: add forgotten "show startup-logs"

The keyword was never documented.

Must be backported in all maintained versions.

(cherry picked from commit f76b3b47ea0c8fc147d614bf4982d15e7de2aa65)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit a9ba03ae8987876304448c84d1adbc25a71d8411)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 323a088ad7831fafd7375dd84ff8c26a27bdff3d)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/doc/management.txt b/doc/management.txt
index 56e4f66..56f119e 100644
--- a/doc/management.txt
+++ b/doc/management.txt
@@ -2919,6 +2919,10 @@
     ecdsa.pem:3 [verify none allow-0rtt ssl-min-ver TLSv1.0 ssl-max-ver TLSv1.3] localhost !www.test1.com
     ecdsa.pem:4 [verify none allow-0rtt ssl-min-ver TLSv1.0 ssl-max-ver TLSv1.3]
 
+show startup-logs
+  Dump all messages emitted during the startup of the current haproxy process,
+  each startup-logs buffer is unique to its haproxy worker.
+
 show table
   Dump general information on all known stick-tables. Their name is returned
   (the name of the proxy which holds them), their type (currently zero, always