Docs updates, small tweaks

src/less/plyr.less

@@ -613,6 +613,20 @@
     line-height: .95;
     -webkit-font-smoothing: subpixel-antialiased;
 }
+// Media duration hidden on small screens
+.plyr__time + .plyr__time {
+    display: none;
+
+    @media (min-width: @plyr-bp-screen-md) {
+        display: inline-block;
+    }
+
+    // Add a slash in before
+    &::before {
+        content: '\2044';
+        margin-right: @plyr-control-spacing;
+    }
+}
 
 // Volume
 // --------------------------------------------------------------