fix a couple of accessibility issues (#115)

This fixes some a11y issues that the firefox a11y helper found.
Basically it hides the burger menu from a11y since it's not needed for
screen readers.

Author: richard-uk1

templates/base.html

@@ -42,7 +42,7 @@
                 <a class="site-title" rel="author" href="/">{{config.title}}</a>
                 <nav class="site-nav">
                     <input type="checkbox" id="nav-trigger" class="nav-trigger">
-                    <label for="nav-trigger">
+                    <label for="nav-trigger" role="none">
                         <span class="menu-icon">
                             <svg viewBox="0 0 18 15" width="18px" height="15px">
                                 <path
@@ -83,11 +83,11 @@ <h2 class="footer-heading">{{config.title}}</h2>
                     <div class="footer-col footer-col-2">
                         <ul class="social-media-list">
                             <li><a href="https://github.com/linebender">
-                                    <svg class="svg-icon">
-                                        <use xlink:href="/minima-social-icons.svg#github"></use>
-                                    </svg>
-                                    <span class="username">linebender</span>
-                                </a></li>
+                                <svg class="svg-icon" role="none">
+                                    <use xlink:href="/minima-social-icons.svg#github"></use>
+                                </svg>
+                                <span class="username">linebender</span>
+                            </a></li>
                         </ul>
                     </div>