feat(darkmode): dark mode toggle (#82)

* feat(darkmode): initial support for dark mode toggle

* fix(darkmode): add svg icons

* feat(darkmode): dispatch onColorSchemeChange event

* add head/darkmode

* feat(darkmode); add colorScheme config

* style: remove empty line

* refactor(darkmode): simplify code

* style: add comment for darkmode config

* i18n support for dark mode toggle

* Some renaming

layouts/partials/sidebar/left.html

@@ -45,5 +45,13 @@
             </a>
         </li>
         {{ end }}
+
+        {{ if (default false .Site.Params.colorScheme.toggle) }}
+            <li id="dark-mode-toggle">
+                {{ partial "helper/icon" "toggle-left" }}
+                {{ partial "helper/icon" "toggle-right" }}
+                <span>{{ T "darkMode" }}</span>
+            </li>
+        {{ end }}
     </ol>
 </aside>