Rename PostCSS files to .pcss (#9013)

* Rename PostCSS files to `.pcss`

* Make Stylelint happy

* Delint

* Rename new files too

* delint

* Fix bad comment placement

res/css/structures/_VideoRoomView.pcss

@@ -0,0 +1,40 @@
+/*
+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.
+*/
+
+.mx_VideoRoomView {
+    flex-grow: 1;
+    min-height: 0;
+
+    display: flex;
+    flex-direction: column;
+    margin: $container-gap-width;
+    margin-right: calc($container-gap-width / 2);
+
+    background-color: $header-panel-bg-color;
+    padding: 8px;
+    border-radius: 8px;
+
+    .mx_AppTile {
+        width: auto;
+        height: 100%;
+        border: none;
+    }
+
+    // While the lobby is shown, the widget needs to stay loaded but hidden in the background
+    .mx_VideoLobby ~ .mx_AppTile {
+        display: none;
+    }
+}