add note

c3simplepage/layouts/shortcodes/note.html

+<p class="note">
+    {{ .Inner | markdownify }}
+</p>

c3simplepage/static/css/c3simplepage.css

@@ -25,6 +25,13 @@ body {
     padding: 15px 20px 20px 60px;
 }
 
+.note {
+    background-image: url('/gfx/note.png');
+    background-repeat: no-repeat;
+    background-position: left;
+    padding: 15px 20px 20px 60px;
+}
+
 pre {
     background-color: lightgray;
     font-family: monospace;