feat: Add country attribute to City

It defaults to "France".

packages/demo/src/App.tsx

@@ -109,6 +109,7 @@
       <TextField source="id" />
       <TextField source="name" />
       <NumberField source="zip_code" />
+      <TextField source="country" />
     </Datagrid>
   </List>
 );
@@ -119,6 +120,7 @@
       <TextField source="id" />
       <TextField source="name" />
       <NumberField source="zip_code" />
+      <TextField source="country" />
       <ReferenceArrayField
         label="Museum"
         reference="Museum"

packages/demo/src/schema.ts

@@ -26,6 +26,7 @@
     City: {
       name: { type: "String", required: true },
       zip_code: { type: "Int" },
+      country: { type: "String", default: "France" },
     },
     Person: {
       name: { type: "String" },