Implement Use Case Selection screen (#8984)

* Introduce new splash page wrapper
* Introduce new use case selection screen

src/settings/Settings.tsx

@@ -698,6 +698,10 @@ export const SETTINGS: {[setting: string]: ISetting} = {
         displayName: _td('Send analytics data'),
         default: null,
     },
+    "FTUE.useCaseSelection": {
+        supportedLevels: LEVELS_ACCOUNT_SETTINGS,
+        default: null,
+    },
     "autocompleteDelay": {
         supportedLevels: LEVELS_DEVICE_ONLY_SETTINGS_WITH_CONFIG,
         default: 200,

src/settings/enums/UseCase.tsx

@@ -0,0 +1,22 @@
+/*
+Copyright 2022 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.
+*/
+
+export enum UseCase {
+    PersonalMessaging = "PersonalMessaging",
+    WorkMessaging = "WorkMessaging",
+    CommunityMessaging = "CommunityMessaging",
+    Skip = "Skip",
+}