Add module declaration for graham_scan

graham_scan/graham_scan.d.ts

@@ -6,3 +6,7 @@ declare class ConvexHullGrahamScan {
     addPoint(x: number, y: number): void;
     getHull(): {x: number, y: number}[];
 }
+
+declare module 'graham_scan' {
+    export = ConvexHullGrahamScan;
+}