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)

assets/sass/pages/_videos.scss

@@ -19,9 +19,12 @@ main#video {
     font-size: 0.85em;
     letter-spacing: -0.005em;
     line-height: 1.5;
-    color: #777777;
     margin: 1.25em 1em 0 1em;
 
+    @include themed() {
+      color: t(color-medium-light);
+    }
+
     a {
       font-weight: bold;
       letter-spacing: 0.001em;
@@ -35,7 +38,6 @@ main#video {
   }
 }
 
-
 // Responsive
 @mixin responsive--videos() {
   main#video {