Declare the minimum supported Minetest version to 5.0.0

This information can be used by ContentDB.

mod.conf

@@ -2,3 +2,4 @@ name = moreores
 description = Adds new ore types.
 depends = default
 optional_depends = carts,farming,frame,mg,toolranks
+min_minetest_version = 5.0.0