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/messages/_EventTileBubble.pcss

@@ -0,0 +1,67 @@
+/*
+Copyright 2019, 2020 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_EventTileBubble {
+    --EventTileBubble_margin-block: 10px; // TODO: Use a spacing variable
+
+    background-color: $dark-panel-bg-color;
+    padding: 10px; // TODO: Use a spacing variable
+    border-radius: 8px;
+    // Reserve space for external timestamps, but also cap the width
+    max-width: min(calc(100% - 2 * $MessageTimestamp_width), 600px);
+    box-sizing: border-box;
+    display: grid;
+    grid-template-columns: 24px minmax(0, 1fr) min-content min-content;
+
+    &::before,
+    &::after {
+        position: relative;
+        grid-column: 1;
+        grid-row: 1 / 3;
+        width: 16px;
+        height: 16px;
+        content: "";
+        inset: 0;
+        mask-repeat: no-repeat;
+        mask-position: center;
+        mask-size: contain;
+        margin-top: $spacing-4;
+    }
+
+    .mx_EventTileBubble_title,
+    .mx_EventTileBubble_subtitle {
+        grid-column: 2;
+        overflow-wrap: break-word;
+    }
+
+    .mx_EventTileBubble_title {
+        font-weight: 600;
+        font-size: $font-15px;
+        grid-row: 1;
+    }
+
+    .mx_EventTileBubble_subtitle {
+        font-size: $font-12px;
+        grid-row: 2;
+    }
+
+    .mx_MessageTimestamp {
+        grid-column: 4;
+        grid-row: 1 / 3;
+        align-self: center;
+        margin-left: $spacing-16;
+    }
+}