Add Keybase social icon (#248)

* Add Keybase social icon

* Fix typo

data/webpack_assets.json

 {
   "app": {
     "js": "js/app.3fc0f988d21662902933.js",
-    "css": "css/app.3f5912c237ddd38c8e76debe081c7ca7.css"
+    "css": "css/app.1cb140d8ba31d5b2f1114537dd04802a.css"
   }
 }

layouts/partials/social-follow.html

   {{- partial "new-window-icon.html" . -}}
 </a>
 {{ end }}
+{{ with .Param "keybase" }}
+<a href="{{ . }}" target="_blank" class="link-transition keybase link dib z-999 pt3 pt0-l mr1" title="Keybase link" rel="noopener" aria-label="follow on Keybase——Opens in a new window">
+  {{ partial "svg/keybase.svg" (dict "size" $icon_size) }}
+  {{- partial "new-window-icon.html" . -}}
+</a>
+{{ end }}
 {{ with .Param "medium" }}
 <a href="{{ . }}" target="_blank" class="link-transition medium link dib z-999 pt3 pt0-l mr1" title="Medium link" rel="noopener" aria-label="follow on Medium——Opens in a new window">
   {{ partial "svg/medium.svg" (dict "size" $icon_size) }}

src/css/_social-icons.css

-.facebook, .twitter, .instagram, .youtube, .github, .gitlab, .linkedin, .medium, .mastodon, .slack, .stackoverflow {
+.facebook, .twitter, .instagram, .youtube, .github, .gitlab, .keybase, .linkedin, .medium, .mastodon, .slack, .stackoverflow {
   fill: #BABABA;
 }
 
   fill: #FC6D26;
 }
 
+.keybase:hover {
+  fill: #3d76ff;
+}
+
 .linkedin:hover {
   fill: #0077b5
 }