Feature(offline): add management module for offline basemaps

src/Utils.ts

@@ -1882,6 +1882,14 @@ In the case that MapComplete is pointed to the testing grounds, the edit will be
         return [].concat(...param)
     }
 
+    public static sum(list: number[]): number {
+        let total = 0
+        for (const number of list) {
+            total += number
+        }
+        return total
+    }
+
     /**
      *
      * JSON.stringify(Utils.reorder({b: "0", a: "1"}, ["a", "b"])) // => '{"a":"1","b":"0"}'