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/views/settings/_IntegrationManager.pcss

@@ -0,0 +1,46 @@
+/*
+Copyright 2015, 2016 OpenMarket Ltd
+
+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_IntegrationManager {
+    .mx_Dialog {
+        box-sizing: border-box;
+        width: 60%;
+        height: 70%;
+        overflow: hidden;
+        max-width: initial;
+        max-height: initial;
+    }
+
+    iframe {
+        background-color: #fff;
+        border: 0;
+        width: 100%;
+        height: 100%;
+    }
+
+    h3 {
+        margin-block: $spacing-20;
+    }
+
+    .mx_IntegrationManager_loading,
+    .mx_IntegrationManager_error {
+        text-align: center;
+    }
+
+    .mx_IntegrationManager_error h3 {
+        color: $alert;
+    }
+}