feat: Show RSS icon if config enables it

This adds support for showing a tiny RSS svg badge in the top menu in
case the user added a menu_item that looks like this:
`{name = "", url = "$BASE_URL/$FEED_FILENAME"}`

This also requires that the user has a config.toml that contains the
following entries:

generate_feed = true
feed_filename = "rss.xml"
author = "your name here"

templates/macros/menu.html

@@ -38,11 +38,26 @@
             <ul class="menu__inner">
             {%- for item in menu_items %}
                 <li {%- if current_item and current_item == item %} class="active" {%- endif %}>
+
                     {%- if item.newtab -%}
                         <a href="{{ item.url | replace(from="$BASE_URL", to=config.base_url) | safe }}" target="_blank" rel="noopener noreferrer">{{ item.name | safe }}</a>
                     {%- else -%}
                         <a href="{{ item.url | replace(from="$BASE_URL", to=config.base_url) | safe }}">{{ item.name | safe }}</a>
                     {%- endif -%}
+
+                    <!-- RSS -->
+                    {%- set is_rss = item.url == "$BASE_URL/$FEED_FILENAME" -%}
+
+                    {%- if is_rss %}
+                        <a type="application/rss+xml" title="RSS" href="{{ get_url(path=config.feed_filename) | safe }}">
+                            <svg width="12" height="12" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512">
+                                <!--!Font Awesome Free 6.5.2 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free Copyright 2024 Fonticons, Inc.-->
+                                <path fill="#ee802f" d="M128.1 416c0 35.4-28.7 64-64 64S0 451.3 0 416s28.7-64 64-64 64 28.7 64 64zm175.7 47.3c-8.4-154.6-132.2-278.6-287-287C7.7 175.8 0 183.1 0 192.3v48.1c0 8.4 6.5 15.5 14.9 16 111.8 7.3 201.5 96.7 208.8 208.8 .5 8.4 7.6 14.9 16 14.9h48.1c9.1 0 16.5-7.7 16-16.8zm144.2 .3C439.6 229.7 251.5 40.4 16.5 32 7.5 31.7 0 39 0 48v48.1c0 8.6 6.8 15.6 15.5 16 191.2 7.8 344.6 161.3 352.5 352.5 .4 8.6 7.4 15.5 16 15.5h48.1c9 0 16.3-7.5 16-16.5z"/>
+                            </svg>
+                        </a>
+                    </p>
+                    {% endif -%}
+
                 </li>
             {% endfor -%}
             </ul>