examples: Fixed HTML output with multi-paragraph READMEs.

examples/template.html

@@ -9,7 +9,7 @@
 
     <meta property="og:type" content="website">
     <meta property="og:title" content="@project_name@ Example: @category_name@/@example_name@">
-    <meta property="og:description" content="@description@">
+    <meta property="og:description" content="@short_description@">
     <meta property="og:image" content="@preview_image@" />
 
     <link rel="stylesheet" type="text/css" href="/@project_name@/examples.css" />