Shell + page loading

And:
- some basic stylesheet i found for basic html elements
- a global lua method for navigating pages

assets/pages/lua-test.rml

@@ -0,0 +1,5 @@
+<div id="page-root">
+    <h1>Lua test page</h1>
+    <p>This button uses <code>NavigateTo('about')</code> lua code instead of a registered C++ event</p>
+    <button onclick="NavigateTo('about')">Go to About Page</button>
+</div>