RewriteEngine On
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteRule ^(.*) index.php?pagina=$1

$url = (isset($_GET['pagina'])) ? $_GET['pagina'] : 'inicio';
$explode = array_filter(explode('/', $url));

$pags = 'pages/';
$ext = '.php';

if(file_exists($pags.$explode['0'].$ext)){
    include($pags.$explode['0'].$ext);
}else{
    echo "Página Não encontrada!";
}

<li class="nav-item dropdown">
    <a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
        <span class="no-icon">Configuração</span>
    </a>
    <div class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
        <a class="dropdown-item" href="/contas/adicionar">Adicionar</a>
        <a class="dropdown-item" href="?page=contas&config=editar">Editar/Apagar</a>
        <!-- <a class="dropdown-item" href="#"></a>
        <a class="dropdown-item" href="#"></a> -->
        <div class="divider"></div>
        <a class="dropdown-item" href="../pages/api.php?action=write">Sincronizar</a>
    </div>
</li>