docs: Mention that dbupdate is sometimes required after changing config.

Signed-off-by: Ben Sturmfels <ben@sturm.com.au>

AUTHORS

@@ -100,6 +100,7 @@ Thank you!
 * Rasmus Larsson
 * Robert Smith
 * Rodney Ewing
+* Rodrigo Martins
 * Rodrigo Rodrigues da Silva
 * Romain Porte
 * Runar Petursson

docs/source/siteadmin/configuration.rst

@@ -59,6 +59,11 @@ read and reference:
   option that we didn't tell you about. :)
 
 
+Enabling extra media types or plugins may require an update to the database, so
+after making changes, it is also a good idea to run::
+
+  $ ./bin/gmg dbupdate
+
 
 Common changes
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