Update PBXProject known_regions attribute to include 'Base' to match project files created using Xcode 11.1

Author: liamnichols

lib/xcodeproj/project/object/root_object.rb

@@ -42,7 +42,7 @@ class PBXProject < AbstractObject
 
         # @return [Array<String>] the list of known regions.
         #
-        attribute :known_regions, Array, ['en']
+        attribute :known_regions, Array, %w(en Base)
 
         # @return [PBXGroup] the main group of the project. The one displayed
         #         by Xcode in the Project Navigator.

spec/project/object/root_object_spec.rb

@@ -32,7 +32,7 @@ module ProjectSpecs
     end
 
     it 'returns the known regions' do
-      @root_object.known_regions.should == %w(en)
+      @root_object.known_regions.should == %w(en Base)
     end
 
     it 'returns the main group' do