Allow Element Call to be started without audio / video interface (#924)

* config: add feature in `config.json`

* groupCall: adjust connection state in feed if allowCallWithoutVideoAndAudio

* matrix-js-sdk: update version for allowCallWithoutVideoAndAudio

- I modified the SDK so that mute unmute work without media and check device permission inside the SDK
- allowCallWithoutVideoAndAudio is only checked at one point outside the SDK

* docu: add join group call without media docu in READMe

---------

Co-authored-by: Robin Townsend <robin@robin.town>
Co-authored-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/matrix-utils.ts

@@ -92,10 +92,14 @@ export async function initClient(
     indexedDB = window.indexedDB;
   } catch (e) {}
 
-  const storeOpts = {} as ICreateClientOpts;
+  const baseOpts = {
+    fallbackICEServerAllowed: fallbackICEServerAllowed,
+    isVoipWithNoMediaAllowed:
+      Config.get().features?.feature_group_calls_without_video_and_audio,
+  } as ICreateClientOpts;
 
   if (indexedDB && localStorage) {
-    storeOpts.store = new IndexedDBStore({
+    baseOpts.store = new IndexedDBStore({
       indexedDB: window.indexedDB,
       localStorage,
       dbName: SYNC_STORE_NAME,
@@ -107,7 +111,7 @@ export async function initClient(
         : () => new IndexedDBWorker(),
     });
   } else if (localStorage) {
-    storeOpts.store = new MemoryStore({ localStorage });
+    baseOpts.store = new MemoryStore({ localStorage });
   }
 
   // Check whether we have crypto data store. If we are restoring a session
@@ -139,14 +143,14 @@ export async function initClient(
   }
 
   if (indexedDB) {
-    storeOpts.cryptoStore = new IndexedDBCryptoStore(
+    baseOpts.cryptoStore = new IndexedDBCryptoStore(
       indexedDB,
       CRYPTO_STORE_NAME
     );
   } else if (localStorage) {
-    storeOpts.cryptoStore = new LocalStorageCryptoStore(localStorage);
+    baseOpts.cryptoStore = new LocalStorageCryptoStore(localStorage);
   } else {
-    storeOpts.cryptoStore = new MemoryCryptoStore();
+    baseOpts.cryptoStore = new MemoryCryptoStore();
   }
 
   // XXX: we read from the URL params in RoomPage too:
@@ -160,7 +164,7 @@ export async function initClient(
   }
 
   const client = createClient({
-    ...storeOpts,
+    ...baseOpts,
     ...clientOptions,
     useAuthorizationHeader: true,
     // Use a relatively low timeout for API calls: this is a realtime app