add TextEncoder/Decoder polyfill to legacy bundle

package.json

@@ -51,6 +51,7 @@
     "another-json": "^0.2.0",
     "base64-arraybuffer": "^0.2.0",
     "bs58": "^4.0.1",
-    "olm": "https://packages.matrix.org/npm/olm/olm-3.1.4.tgz"
+    "olm": "https://packages.matrix.org/npm/olm/olm-3.1.4.tgz",
+    "text-encoding": "^0.7.0"
   }
 }

scripts/post-install.mjs

@@ -87,6 +87,9 @@ async function populateLib() {
         path.join(modulesDir, 'base64-arraybuffer/lib/base64-arraybuffer.js'),
         path.join(libDir, "base64-arraybuffer/index.js")
     );
+    // this probably should no go in here, we can just import "aes-js" from legacy-extras.js
+    // as that file is never loaded from a browser
+    
     // transpile aesjs to esm
     await fs.mkdir(path.join(libDir, "aes-js/"));
     await commonjsToESM(

src/legacy-polyfill.js

@@ -18,6 +18,13 @@ limitations under the License.
 import "core-js/stable";
 import "regenerator-runtime/runtime";
 import "mdn-polyfills/Element.prototype.closest";
+// olm.init needs utf-16le, and this polyfill was
+// the only one I could find supporting it.
+// TODO: because the library sees a commonjs environment,
+// it will also include the file supporting *all* the encodings,
+// weighing a good extra 500kb :-(
+import "text-encoding";
+
 // TODO: contribute this to mdn-polyfills
 if (!Element.prototype.remove) {
     Element.prototype.remove = function remove() {

yarn.lock

@@ -1864,6 +1864,11 @@ supports-color@^6.1.0:
   dependencies:
     has-flag "^3.0.0"
 
+text-encoding@^0.7.0:
+  version "0.7.0"
+  resolved "https://registry.yarnpkg.com/text-encoding/-/text-encoding-0.7.0.tgz#f895e836e45990624086601798ea98e8f36ee643"
+  integrity sha512-oJQ3f1hrOnbRLOcwKz0Liq2IcrvDeZRHXhd9RgLrsT+DjWY/nty1Hi7v3dtkaEYbPYe0mUoOfzRrMwfXXwgPUA==
+
 to-fast-properties@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/to-fast-properties/-/to-fast-properties-2.0.0.tgz#dc5e698cbd079265bc73e0377681a4e4e83f616e"