Schema: support other mp_ keys too

In addition to the mp_village_gold used in mainline,
there exist as well:
- mp_fog
- mp_shroud
- mp_village_support

data/schema/core/addons.cfg

@@ -572,7 +572,10 @@
 	#{BASE_COMPATIBILITY_KEYS}
 	{SIMPLE_KEY force_modification string_list}
 	{SIMPLE_KEY require_scenario bool}
+	{SIMPLE_KEY mp_fog bool}
+	{SIMPLE_KEY mp_shroud bool}
 	{SIMPLE_KEY mp_village_gold int}
+	{SIMPLE_KEY mp_village_support int}
 	{SIMPLE_KEY define string}
 	{SIMPLE_KEY carryover_report bool}
 	{LINK_TAG "era/options"}