DOC: Add tune.h2.max-frame-size option to table of contents

This option was introduced in a24b35ca18885809001454699b4e44b49abccde6, which
is 2.0+. It should be backported as far as it easily applies.

(cherry picked from commit 6a8638ff5341939fd6a236725d466f3b9eadcc9d)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
(cherry picked from commit bf7493e388a7d559bae5c543f13cb434296c7891)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
(cherry picked from commit fb7183504c81cb18b08c13368409a68e613bc9cf)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
(cherry picked from commit f89a835b1f6a76992212740ea7faf8f25dd320da)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/doc/configuration.txt b/doc/configuration.txt
index b29ba13..ee3dfcf 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -1089,6 +1089,7 @@
    - tune.h2.header-table-size
    - tune.h2.initial-window-size
    - tune.h2.max-concurrent-streams
+   - tune.h2.max-frame-size
    - tune.http.cookielen
    - tune.http.logurilen
    - tune.http.maxhdr