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/auth/_AuthFooter.pcss

@@ -0,0 +1,31 @@
+/*
+Copyright 2019 New Vector 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_AuthFooter {
+    text-align: center;
+    width: 100%;
+    font-size: $font-14px;
+    opacity: 0.72;
+    padding: 20px 0;
+    background: linear-gradient(rgba(0, 0, 0, 0), rgba(0, 0, 0, 0.8));
+}
+
+.mx_AuthFooter a:link,
+.mx_AuthFooter a:hover,
+.mx_AuthFooter a:visited {
+    color: $accent-fg-color;
+    margin: 0 22px;
+}