Add basic PWA config - will setup later

Author: philwareham

_config.yml

@@ -21,3 +21,16 @@ highlighter: none
 keep_files: [
   'expect-ct-report'
 ]
+pwa:
+  enabled: false # Optional
+  sw_src_filepath: service-worker.js # Optional
+  sw_dest_filename: service-worker.js # Optional
+  dest_js_directory: assets/js # Required
+  precache_recent_posts_num: 5 # Optional
+  precache_glob_directory: / # Optional
+  precache_glob_patterns: # Optional
+    - "{js,css,fonts}/**/*.{js,css,eot,svg,ttf,woff}"
+    - index.html
+  precache_glob_ignores: # Optional
+    - sw-register.js
+    - "fonts/**/*"