FIX: white band between navbar and main

templates/menu.html

-<nav class="navbar is-fixed-top has-shadow" role="navigation" aria-label="main navigation" id="main-navbar">
+<nav class="navbar is-fixed-top" role="navigation" aria-label="main navigation" id="main-navbar">
     <input type="checkbox" id="burger-toggle" role="button" class="navbar-toggle" aria-label="menu" aria-expanded="false" data-target="main-menu" />
     <div class="navbar-brand">
         <a href="{{ get_url(path="@/_index.md") }}" class="navbar-item">