styleguide: Add WIP message

styleguide/demopage/index.html

@@ -36,6 +36,15 @@
             </ul>
         </nav>
         <main>
+            <div class="alert">
+                <i data-icon="warning"></i>
+                <p>
+                    <strong>Work in progress</strong>
+                    This style guide is still under development.<br>
+                    Not all resources may be available yet, explanations and examples may be missing and things may
+                    change without notice.
+                </p>
+            </div>
             <h1>Testdocument</h1>
             <p>Tests for Fonts and Colorpalettes</p>