Move voice message components to audio-generic directory

res/css/views/audio_messages/_Waveform.scss

@@ -0,0 +1,40 @@
+/*
+Copyright 2021 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_Waveform {
+    position: relative;
+    height: 30px; // tallest bar can only be 30px
+    top: 1px; // because of our border trick (see below), we're off by 1px of aligntment
+
+    display: flex;
+    align-items: center; // so the bars grow from the middle
+
+    overflow: hidden; // this is cheaper than a `max-height: calc(100% - 4px)` in the bar's CSS.
+
+    // A bar is meant to be a 2x2 circle when at zero height, and otherwise a 2px wide line
+    // with rounded caps.
+    .mx_Waveform_bar {
+        width: 0; // 0px width means we'll end up using the border as our width
+        border: 1px solid transparent; // transparent means we'll use the background colour
+        border-radius: 2px; // rounded end caps, based on the border
+        min-height: 0; // like the width, we'll rely on the border to give us height
+        max-height: 100%; // this makes the `height: 42%` work on the element
+        margin-left: 1px; // we want 2px between each bar, so 1px on either side for balance
+        margin-right: 1px;
+
+        // background color is handled by the parent components
+    }
+}