Rename switch_package_to_release.js to .cjs

Slightly surprisingly, the symlink is enough to make `node
switch_package_to_release.js` work.

scripts/switch_package_to_release.cjs

@@ -0,0 +1,22 @@
+#!/usr/bin/env node
+
+const fsProm = require("fs/promises");
+
+const PKGJSON = "package.json";
+
+async function main() {
+    const pkgJson = JSON.parse(await fsProm.readFile(PKGJSON, "utf8"));
+    for (const field of ["main", "typings"]) {
+        if (pkgJson["matrix_lib_" + field] !== undefined) {
+            pkgJson[field] = pkgJson["matrix_lib_" + field];
+        }
+    }
+
+    // matrix-js-sdk is built into ECMAScript modules. Make sure we declare it as such.
+    // See https://nodejs.org/api/packages.html#type.
+    pkgJson["type"] = "module";
+
+    await fsProm.writeFile(PKGJSON, JSON.stringify(pkgJson, null, 2));
+}
+
+main();

scripts/switch_package_to_release.js

@@ -0,0 +1 @@
+switch_package_to_release.cjs