Add header indicating draft status

Author: marijnh

html/index.html

@@ -6,6 +6,10 @@
   <link rel=stylesheet href="css/ejs.css">
 </head>
 
+<div style="background: #ff9; border-bottom: 1px solid silver; padding: 6px 4em; text-align: center">
+  This is a draft of Eloquent JavaScript's 3rd edition. Thanks for taking a look! If you spot a problem, please <a href="mailto:[email protected]">email me</a> or <a href="https://github.com/marijnh/Eloquent-JavaScript/issues">open an issue</a>.
+</div>
+
 <article>
   <h1>Eloquent JavaScript<div style="font-size: 70%">third edition</div></h2>
 

src/chapter.html

@@ -16,6 +16,10 @@
   <</if>>
 </head>
 
+<div style="background: #ff9; border-bottom: 1px solid silver; padding: 6px 4em; text-align: center">
+  This is a draft of Eloquent JavaScript's 3rd edition. Thanks for taking a look! If you spot a problem, please <a href="mailto:[email protected]">email me</a> or <a href="https://github.com/marijnh/Eloquent-JavaScript/issues">open an issue</a>.
+</div>
+
 <article>
 <nav>
   <<if $in.prev_link>><a href="<<t $in.prev_link>>.html" title="previous chapter">◀</a> <</if>>