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/index.headers

@@ -5,10 +5,17 @@
   X-Frame-Options: sameorigin
   X-XSS-Protection: 1; mode=block
 
-# Super long cache (one year) for vendored assets: web fonts, emojis, etc.
+# Super long cache (one year) for vendored assets:
+# web fonts, emojis, etc.
 /vendor/*
   Cache-Control: max-age=31536000, public, immutable
 
+# Kinda long cache (one day) for CSS, JS:
+/css/*
+  Cache-Control: max-age=86400, public, immutable
+/js/*
+  Cache-Control: max-age=86400, public, immutable
+
 # Proper MIME type for Atom feed
 /*.atom
   Content-Type: application/atom+xml