title: Add a button to Leaflet map and style it like the original buttons
body: <p>Codepen: <a href="https://codepen.io/anon/pen/vmbmqK?editors=1011" rel="nofollow noreferrer">https://codepen.io/anon/pen/vmbmqK?editors=1011</a></p>
  
  <p>I tried reusing the original Leaflet classes (instead of repeating their CSS), but their CSS has a <code>:a</code>, while Bootstrap's modal requires a button and won't work with an anchor. The hacky way around this would be to use an anchor and listen to the click to manually open the Bootstrap modal with Javascript, but I'd like to hear other [better] options.</p>
  
  <p>At risk of being told to make another question (in which case I'll remove this paragraph altogether since it's not too important), I'd also like to look into whether or not this part of the code can be replaced with something more straightforward, especially the <code>'onAdd': () =&gt; {return</code>:</p>
  
  <pre><code>let filterButton = L.Control.extend({
    'onAdd': () =&gt; {
      return $(`
  &lt;button type="button" class="btn btn-secondary" data-toggle="modal" data-target="#exampleModal"&gt;
  Filter
  &lt;/button&gt;
  `)[0];
    },
  });
  </code></pre>