Update documentation

_static/copybutton.css

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+/* Copy buttons */
+a.copybtn {
+    position: absolute;
+    top: .2em;
+    right: .2em;
+    width: 1em;
+    height: 1em;
+	opacity: .3;
+    transition: opacity 0.5s;
+    border: none;
+    user-select: none;
+}
+
+div.highlight  {
+    position: relative;
+}
+
+a.copybtn > img {
+    vertical-align: top;
+    margin: 0;
+    top: 0;
+    left: 0;
+    position: absolute;
+}
+
+.highlight:hover .copybtn {
+	opacity: 1;
+}
+
+/**
+ * A minimal CSS-only tooltip copied from:
+ *   https://codepen.io/mildrenben/pen/rVBrpK
+ *
+ * To use, write HTML like the following:
+ *
+ * <p class="o-tooltip--left" data-tooltip="Hey">Short</p>
+ */
+ .o-tooltip--left {
+  position: relative;
+ }
+
+ .o-tooltip--left:after {
+    opacity: 0;
+    visibility: hidden;
+    position: absolute;
+    content: attr(data-tooltip);
+    padding: 2px;
+    top: 0;
+    left: -.2em;
+    background: grey;
+    font-size: 1rem;
+    color: white;
+    white-space: nowrap;
+    z-index: 2;
+    border-radius: 2px;
+    transform: translateX(-102%) translateY(0);
+    transition: opacity 0.2s cubic-bezier(0.64, 0.09, 0.08, 1), transform 0.2s cubic-bezier(0.64, 0.09, 0.08, 1);
+}
+
+.o-tooltip--left:hover:after {
+    display: block;
+    opacity: 1;
+    visibility: visible;
+    transform: translateX(-100%) translateY(0);
+    transition: opacity 0.2s cubic-bezier(0.64, 0.09, 0.08, 1), transform 0.2s cubic-bezier(0.64, 0.09, 0.08, 1);
+    transition-delay: .5s;
+}