Add webmail link

config/default.json5

@@ -2,6 +2,7 @@
     app: {
         name: 'Rainbox Email',
         contact_email: 'contact@rainbox.email',
+        webmail_url: 'https://rc.rainbox.email',
     },
     log_level: "DEV",
     db_log_level: "ERROR",

views/layouts/base.njk

@@ -17,6 +17,7 @@
         <button id="menu-button"><i data-feather="menu"></i></button>
         <ul id="main-menu">
             <li><a href="{{ route('about') }}"><i data-feather="info"></i> <span class="tip">About</span></a></li>
+            <li><a href="{{ app.webmail_url }}" target="_blank"><i data-feather="mail"></i> <span class="tip">Webmail</span></a></li>
             {% if user %}
                 {% if user.is_admin %}
                     <li><a href="{{ route('backend') }}"><i data-feather="settings"></i> <span class="tip">Backend</span></a></li>