Conform more of the codebase with noImplicitAny and strictNullChecks (#25174

* Conform more of the codebase with `noImplicitAny` and `strictNullChecks`

* Fix tests

* Update src/vector/app.tsx

src/@types/jitsi-meet.d.ts

@@ -0,0 +1,29 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import "jitsi-meet";
+
+declare module "jitsi-meet" {
+    interface ExternalAPIEventCallbacks {
+        errorOccurred: (e: { error: Error & { isFatal?: boolean } }) => void;
+    }
+
+    interface JitsiMeetExternalAPI {
+        executeCommand(command: "setTileView", value: boolean): void;
+    }
+}
+
+export as namespace Jitsi;