dark mode 😎 (#112)

* prepare dark mode stuffs

* themed all global colors

* store preference in local storage

* toggle styling

* lightbulb position

* minify bundled script with uglify-js instead of hugo

* detect whether user has an OS-wide dark mode preference and use that by default

* two different colors for each homepage link

* inline bulb SVGs into stylesheet

* fingerprint and cache styles for a year

* fix lightbulb positioning with weird magic numbers, will come back to that

* themed syntax highlighting

* use terser instead of uglify-js (b/c of ES6)

layouts/partials/page/header.html

@@ -8,6 +8,7 @@
       {{- range .Site.Menus.main }}
       <li><a class="no-underline" {{ printf "href=%q" .URL | safeHTMLAttr }} aria-label="{{ .Name }}"{{ if strings.HasPrefix .URL "http" }} target="_blank" rel="me noopener"{{ end }}><span class="icon">{{ .Pre }}</span><span class="text">{{ .Name }}</span></a></li>
       {{ end -}}
+      <li><button id="dark-mode-toggle" title="Toggle Dark Mode" aria-label="Toggle Dark Mode"></button></li>
     </ul>
   </nav>
 </header>