Add codeblock buttons

Summary: Shamelessly ripped off from docusaurus.io

Reviewed By: jknoxville

Differential Revision: D15123501

fbshipit-source-id: 10451c72494e022af5887d4c78ef0db1ff581254

website/static/css/code-blocks-buttons.css

@@ -0,0 +1,46 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/* "Copy" code block button */
+pre {
+  position: relative;
+}
+
+pre .btnIcon {
+  position: absolute;
+  top: 4px;
+  z-index: 2;
+  cursor: pointer;
+  border: 1px solid transparent;
+  padding: 0;
+  color: #222;
+  background-color: transparent;
+  height: 30px;
+  transition: all 0.25s ease-out;
+}
+
+pre .btnIcon:hover {
+  text-decoration: none;
+}
+
+.btnIcon__body {
+  align-items: center;
+  display: flex;
+}
+
+.btnIcon svg {
+  fill: currentColor;
+  margin-right: 0.4em;
+}
+
+.btnIcon__label {
+  font-size: 11px;
+}
+
+.btnClipboard {
+  right: 10px;
+}