add minimal shim stubs for v2 backwards compatibility

js/v2.ts

@@ -0,0 +1,43 @@
+import { Header, Cache, RangeResponse } from './v3';
+
+async function getHeaderAndRoot(a:ArrayBuffer, etag?:string): Promise<[Header, [string, number, ArrayBuffer]]> {
+	const header = {
+		specVersion: 2,
+		rootDirectoryOffset: 0,
+		rootDirectoryLength: 0,
+		jsonMetadataOffset: 0,
+		jsonMetadataLength: 0,
+		leafDirectoryOffset: 0,
+		leafDirectoryLength: undefined,
+		tileDataOffset: 512000,
+		tileDataLength: undefined,
+		numAddressedTiles: 0,
+		numTileEntries: 0,
+		numTileContents: 0,
+		clustered: false,
+		internalCompression: 0,
+		tileCompression: 0,
+		tileType: 0,
+		minZoom: 0,
+		maxZoom: 0,
+		minLon: 0,
+		minLat: 0,
+		maxLon: 0,
+		maxLat: 0,
+		centerZoom: 0,
+		centerLon: 0,
+		centerLat: 0,
+		etag: etag,
+	};	
+	return [header, ["",0,new ArrayBuffer(0)]];
+}
+
+async function getZxy(header:Header,cache:Cache): Promise<RangeResponse | undefined> {
+	return Promise.resolve(undefined);
+}
+
+export default {
+	getHeaderAndRoot: getHeaderAndRoot,
+	getZxy: getZxy
+};
+