js: Mirror decodeVertexV1Deltas test from native code

This test has the same data as the correponding test from demo/tests.cpp
and expands testing coverage for 16-bit delta decoding that V1_Custom
test was previously lacking.

Author: zeux

js/meshopt_decoder.test.js

@@ -99,6 +99,25 @@ var tests = {
 		assert.deepStrictEqual(result, expected);
 	},
 
+	decodeVertexBufferV1_Deltas: function () {
+		var encoded = new Uint8Array([
+			0xa1, 0x99, 0x99, 0x01, 0x2a, 0xaa, 0xaa, 0xaa, 0x02, 0x04, 0x44, 0x44, 0x44, 0x43, 0x33, 0x33, 0x33, 0x02, 0x06, 0x66, 0x66, 0x66, 0x66,
+			0x66, 0x66, 0x66, 0x02, 0x08, 0x88, 0x88, 0x88, 0x87, 0x77, 0x77, 0x77, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0xf8, 0x00, 0xf8, 0x00, 0xf0, 0x00, 0xf0, 0x00, 0x01, 0x01,
+		]);
+
+		var expected = new Uint16Array([
+			248, 248, 240, 240, 249, 250, 243, 244, 250, 252, 246, 248, 251, 254, 249, 252, 252, 256, 252, 256, 253, 258, 255, 260, 254, 260, 258,
+			264, 255, 262, 261, 268, 256, 264, 264, 272, 257, 262, 267, 268, 258, 260, 270, 264, 259, 258, 273, 260, 260, 256, 276, 256, 261, 254,
+			279, 252, 262, 252, 282, 248, 263, 250, 285, 244,
+		]);
+
+		var result = new Uint16Array(expected.length);
+		decoder.decodeVertexBuffer(new Uint8Array(result.buffer), 16, 8, encoded);
+
+		assert.deepStrictEqual(result, expected);
+	},
+
 	decodeIndexBuffer16: function () {
 		var encoded = new Uint8Array([
 			0xe0, 0xf0, 0x10, 0xfe, 0xff, 0xf0, 0x0c, 0xff, 0x02, 0x02, 0x02, 0x00, 0x76, 0x87, 0x56, 0x67, 0x78, 0xa9, 0x86, 0x65, 0x89, 0x68, 0x98,