Add dialpad to transfer dialog + various dialpad UI improvements (#6363)

Co-authored-by: Germain <germain@souquet.com>
Co-authored-by: Andrew Morgan <andrew@amorgan.xyz>
Co-authored-by: David Baker <dbkr@users.noreply.github.com>

src/dispatcher/payloads/TransferCallPayload.ts

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+/*
+Copyright 2021 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 { ActionPayload } from "../payloads";
+import { Action } from "../actions";
+import { MatrixCall } from "matrix-js-sdk/src/webrtc/call";
+
+export interface TransferCallPayload extends ActionPayload {
+    action: Action.TransferCallToMatrixID | Action.TransferCallToPhoneNumber;
+    // The call to transfer
+    call: MatrixCall;
+    // Where to transfer the call. A Matrix ID if action == TransferCallToMatrixID
+    // and a phone number if action == TransferCallToPhoneNumber
+    destination: string;
+    // If true, puts the current call on hold and dials the transfer target, giving
+    // the user a button to complete the transfer when ready.
+    // If false, ends the call immediately and sends the user to the transfer
+    // destination
+    consultFirst: boolean;
+}