Improve design of the rich text editor (#9533)

New design for rich text composer

res/css/views/rooms/_EmojiButton.pcss

@@ -0,0 +1,35 @@
+/*
+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.
+*/
+
+@import "./_MessageComposerButton.pcss";
+
+.mx_EmojiButton {
+    @mixin composerButton 50%,$accent;
+}
+
+.mx_EmojiButton_highlight {
+    @mixin composerButtonHighLight;
+}
+
+.mx_EmojiButton_icon::before {
+    mask-image: url('$(res)/img/element-icons/room/composer/emoji.svg');
+}
+
+.mx_MessageComposer_wysiwyg {
+    .mx_EmojiButton {
+        @mixin composerButton 5px,$tertiary-content;
+    }
+}