[css-easing-2] Define that linear serializes as itself

Author: tabatkins

css-easing-2/Overview.bs

@@ -44,6 +44,23 @@ WPT Display: closed
   }
 }
 </style>
+<style>
+/* Put nice boxes around each algorithm. */
+[data-algorithm]:not(.heading) {
+  padding: .5em;
+  border: thin solid #ddd; border-radius: .5em;
+  margin: .5em calc(-0.5em - 1px);
+}
+[data-algorithm]:not(.heading) > :first-child {
+  margin-top: 0;
+}
+[data-algorithm]:not(.heading) > :last-child {
+  margin-bottom: 0;
+}
+[data-algorithm] [data-algorithm] {
+    margin: 1em 0;
+}
+</style>
 
 Introduction {#introduction}
 ============================
@@ -245,6 +262,8 @@ A [=linear easing function=] has the following syntax:
 <h4 id=linear-easing-function-serializing>
 Serializing</h4>
 
+The ''linear'' keyword is serialized as itself.
+
 <div algorithm>
   To <dfn export>serialize a linear() function</dfn>: