ogpについてtwitterのみhttpになっていたため、httpsに変更

Author: hajihaji9988

_includes/header.html

@@ -24,7 +24,7 @@
   <meta name="twitter:description" content="{{page.description}}">
   <meta name="twitter:title" content="{{ page.j-title }} - {{ page.title }} | DojoCon Japan 2018">
   <meta name="twitter:site" content="@DojoConJapan">
-  <meta name="twitter:image" content="http://dojocon2018.coderdojo.jp/img/og_image_1200x630.png">
+  <meta name="twitter:image" content="https://dojocon2018.coderdojo.jp/img/og_image_1200x630.png">
   <link rel="icon" href="/img/cropped-favicon-32x32.png" sizes="32x32">
   <link rel="icon" href="/img/cropped-favicon-192x192.png" sizes="192x192">
   <link rel="/img/cropped-favicon-180x180.png">
@@ -76,4 +76,4 @@ <h3 class="gnav__title text-center">DojoCon Japan 2018</h3>
                 class="fab fa-facebook-f"></i></a></li>
       </ul>
     </div>
-  </section>
+  </section>