Add syntax highlighting helpers for Emacs

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

doc/conditions.md

@@ -123,3 +123,9 @@ Therefore, any plugin that supplies Finit with conditions must ensure
 that their state is updated after each reconfiguration.  This can be
 done by binding to the `HOOK_SVC_RECONF` hook.  For an example of how
 to do this, see `plugins/pidfile.c`.
+
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