modularize playground (prep for persistent/modular file handling)

playground/src/preload.ts

@@ -0,0 +1,21 @@
+import {ZipFile} from './zipfile'
+export let archive: ZipFile | undefined;
+export let preload = (async function () {
+  // We pull down an archive of .ttc and support shim.files
+  try {
+    let res = await self.fetch("files.zip");
+    if (res.status === 200) {
+      let data = await res.arrayBuffer();
+      archive = new ZipFile(new Uint8Array(data));
+      let entries = archive.entries;
+      let count = Object.keys(entries).length;
+      console.log(`preloaded ${count} files`);
+    } else {
+      console.error(
+        `fetch of files.zip got status ${res.status}: ${res.statusText}`
+      );
+    }
+  } catch (e) {
+    console.error("preload failed", e);
+  }
+})();