Tidy and improve dev scripts (#25978)

scripts/build-jitsi.ts

@@ -0,0 +1,30 @@
+// This is a JS script so that the directory is created in-process on Windows.
+// If the script isn't run in-process, there's a risk of it racing or never running
+// due to file associations in Windows.
+// Sorry.
+
+import * as fs from "node:fs";
+import * as path from "node:path";
+import { mkdirpSync } from "mkdirp";
+import fetch from "node-fetch";
+import { ProxyAgent } from "proxy-agent";
+
+console.log("Making webapp directory");
+mkdirpSync("webapp");
+
+// curl -s https://meet.element.io/libs/external_api.min.js > ./webapp/jitsi_external_api.min.js
+console.log("Downloading Jitsi script");
+const fname = path.join("webapp", "jitsi_external_api.min.js");
+
+fetch("https://meet.element.io/libs/external_api.min.js", {
+    agent: new ProxyAgent(),
+})
+    .then((res) => {
+        const stream = fs.createWriteStream(fname);
+        return new Promise<void>((resolve, reject) => {
+            res.body.pipe(stream);
+            res.body.on("error", (err) => reject(err));
+            res.body.on("finish", () => resolve());
+        });
+    })
+    .then(() => console.log("Done with Jitsi download"));