Added download.ts as helper for npm

src/download.ts

@@ -0,0 +1,13 @@
+import { createWriteStream } from 'node:fs';
+import { argv } from 'node:process';
+import { Readable } from 'node:stream';
+import { finished } from 'node:stream/promises';
+
+const url = argv[2];
+const targetFile = argv[3];
+
+console.log(`Downloading ${url} to ${targetFile}`);
+
+const file = createWriteStream(targetFile);
+const { body } = await fetch(url);
+await finished(Readable.fromWeb(<any>body).pipe(file));