Adjust sponsorship layout (#1593)

* Fix SVG being black
    Adobe Illustrator SVGs have rendering problems on PTIO for unknown to
    me reasons. Inkscape works fine.
* Rewrite with plain Flexbox
    Nicer end-user experience than Bootstrap grid

pages/sponsors.html

@@ -7,21 +7,22 @@ permalink: /sponsors/
 <div class="col-12">
   <div class="row">
     <div class="mx-auto text-center">
-      <div class="mt-4 mb-4">
+      <div class="my-4">
         <h1>Sponsors of {{ site.name }}</h1>
       </div>
-      <div class="mt-5 mb-5">
+      <div class="mt-4 mb-3">
         {% include sponsors/gold.html %}
       </div>
       <div class="mb-4">
         <p>The {{ site.name }} website and services are a community project. There is no advertising, affiliate links, or other forms of monetization.<br><strong>Your donations here directly support hosting this website and compensating contributors to this project.</strong></p>
         <p>
-          <a href="https://opencollective.com/privacytoolsio#section-contribute" class="btn btn-success mb-5">Become a Sponsor</a>
-          <a href="/donate/" class="btn btn-outline-danger mb-5"><span class="fas fa-heart fa-fw"></span> Donate Directly</a>
+          <a href="https://opencollective.com/privacytoolsio#section-contribute" class="btn btn-success">Become a Sponsor</a>
+          <a href="/donate/" class="btn btn-outline-danger"><span class="fas fa-heart fa-fw"></span> Donate Directly</a>
         </p>
       </div>
     </div>
   </div>
+
   <h3>Why sponsor {{ site.name }}?</h3>
   <p>This sponsorship program is designed to allow companies, organizations, and individuals partner with the {{ site.name }} team to support our vision of a more privacy-respecting internet and the greater online community.</p>
   <p>With this exposure and sponsorship, your customers will recognize your intrinsic understanding and commitment to user privacy. Moreover, you'll directly contribute to our mission of spreading privacy-respecting tools and knowledge worldwide!</p>