Include 'submit' hook in listing of hooks run synchronously

Appears to be omitted on config.md - see the hooks.md where this is listed
as hook with an ability to prevent a submit, before this has happened.

Change-Id: I446f05c1f2372c92b3bb3dcf2d81a64958c2c3b6

src/main/resources/Documentation/config.md

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 1e5502a..9303587 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -10,11 +10,12 @@
 
 Make sure your hook scripts are executable if running on *nix.
 
-With the exception of the `commit-received` and `ref-update` hooks, hooks are
-run in the background after the relevant change has taken place so are unable
-to affect the outcome of any given change. Because of the fact the hooks are
-run in the background after the activity, a hook might not be notified about
-an event if the server is shutdown before the hook can be invoked.
+With the exception of the `commit-received`, `ref-update` and `submit` hooks,
+hooks are run in the background after the relevant change has taken place so
+are unable to affect the outcome of any given change. Because of the fact the
+hooks are run in the background after the activity, a hook might not be
+notified about an event if the server is shutdown before the hook can be
+invoked.
 
 Configuration
 -------------