add Vector.ZERO and TransformMatrix.IDENTITY

Author: suchipi

packages/2d/src/Models/TransformMatrix.ts

@@ -14,6 +14,8 @@ export function createSVGMatrix(): DOMMatrix {
 
 /** Represents a 2-dimensional transformation matrix. */
 export default class TransformMatrix {
+  static IDENTITY = new TransformMatrix();
+
   _matrix: DOMMatrix;
 
   /** Create a TransformMatrix from a DOMMatrix of SVGMatrix. */

packages/2d/src/Models/Vector.ts

@@ -4,6 +4,8 @@
  * A two-dimensional vector, used to represent points, sizes, and more.
  */
 export default class Vector {
+  static ZERO: ReadOnlyVector = new Vector(0, 0);
+
   x: number;
   y: number;