Add a language switcher to the navigation

This ignores whether the current page has a translation in a
given language, but it's a start.

i18n/en.yaml

@@ -25,6 +25,8 @@
 # Navigation
 - id: toggleNavigation
   translation: "Toggle navigation"
+- id: languageSwitcherLabel
+  translation: "Language"
 - id: gcseLabelShort
   translation: "Search"
 - id: gcseLabelLong

layouts/partials/nav.html

@@ -28,6 +28,30 @@
             </li>
           {{ end }}
         {{ end }}
+
+        {{ if .Site.IsMultiLingual }}
+          {{ if ge (len .Site.Languages) 3 }}
+            <li class="navlinks-container">
+              <a class="navlinks-parent" href="javascript:void(0)">{{ i18n "languageSwitcherLabel" }}</a>
+              <div class="navlinks-children">
+                {{ range .Site.Languages }}
+                  {{ if not (eq .Lang $.Site.Language.Lang) }}
+                    <a href="/{{ .Lang }}">{{ default .Lang .LanguageName }}</a>
+                  {{ end }}
+                {{ end }}
+              </div>
+            </li>
+          {{ else }}
+            <li>
+              {{ range .Site.Languages }}
+                {{ if not (eq .Lang $.Site.Language.Lang) }}
+                  <a href="/{{ .Lang }}">{{ default .Lang .LanguageName }}</a>
+                {{ end }}
+              {{ end }}
+            </li>
+          {{ end }}
+        {{ end }}
+
         {{ if isset .Site.Params "gcse" }}
           <li>
             <a href="#modalSearch" data-toggle="modal" data-target="#modalSearch" style="outline: none;">