Add test case

codecs/visdif/package.json

@@ -1,5 +1,6 @@
 {
   "name": "avif",
+  "type": "module",
   "scripts": {
     "build": "../build-cpp.sh"
   }

codecs/visdif/test.mjs

@@ -0,0 +1,22 @@
+
+import {dirname} from "path";
+globalThis.__dirname = dirname(import.meta.url);
+import { createRequire } from 'module';
+
+globalThis.require = createRequire(import.meta.url);
+import visdif from './visdif.js';
+
+const {VisDiff} = await visdif({
+	locateFile() {
+		return new URL("./visdif.wasm", import.meta.url).pathname;
+	}
+});
+
+const comparator = new VisDiff(
+	new Uint8ClampedArray([0, 0, 0, 255]),
+	1,	
+	1
+);
+
+const distance = comparator.distance(new Uint8ClampedArray([1,1,1,255]));
+console.log({distance});