Allow template element to provide content to label

This provides one of several options a user can implement in order to
get a custom button.

plugins/toolbar/index.html

@@ -32,6 +32,14 @@ <h1>How to use</h1>
 
 	<pre><code class="language-markup" data-label="Hello World!">&lt;pre data-src=&quot;plugins/toolbar/prism-toolbar.js&quot; data-label=&quot;Hello World!&quot;&gt;&lt;/pre&gt;</code></pre>
 
+	<p>If you want to provide arbitrary HTML to the label, create a <code>template</code> element with the HTML you want in the label, and provide the
+		<code>template</code> element's <code>id</code> to <code>data-label</code>. The Toolbar plugin will use the template's content for the button.
+		You can also use to declare your event handlers inline:</p>
+
+	<pre><code class="language-markup" data-label="my-label-button">&lt;pre data-src=&quot;plugins/toolbar/prism-toolbar.js&quot; data-label=&quot;Hello World!&quot;&gt;&lt;/pre&gt;</code></pre>
+
+	<pre><code>&lt;template&gt;&lt;button onclick=&quot;myFunction();&quot;&gt;My button&lt;button&gt;&lt;/template&gt;</code></pre>
+
 	<p>For more flexibility, the Toolbar exposes a JavaScript function that can be used to register new buttons or labels to the Toolbar,
 		<code>Prism.plugins.toolbar.registerButton</code>.</p>
 

plugins/toolbar/prism-toolbar.js

@@ -98,18 +98,22 @@
 			return;
 		}
 
-		var text = pre.getAttribute('data-label');
-
 		var element;
+		var text = pre.getAttribute('data-label');
+		var template = document.querySelector('template#' + text);
 
-		if (pre.hasAttribute('data-url')) {
-			element = document.createElement('a');
-			element.href = pre.getAttribute('data-url');
+		if (template) {
+			element = template.content;
 		} else {
-			element = document.createElement('span');
-		}
+			if (pre.hasAttribute('data-url')) {
+				element = document.createElement('a');
+				element.href = pre.getAttribute('data-url');
+			} else {
+				element = document.createElement('span');
+			}
 
-		element.textContent = text;
+			element.innerHTML = text;
+		}
 
 		return element;
 	});