Prepare preliminary PWA support

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

static/manifest.webmanifest

@@ -0,0 +1,18 @@
+{
+  "name": "Harsh Shandilya's blog",
+  "short_name": "msfjarvis.website",
+  "description": "Thoughts and ramblings of a young software developer",
+  "start_url": "/posts",
+  "background_color": "#292a2d",
+  "theme_color": "#a9a9b3",
+  "icons": [{
+    "src": "favicon-16x16.png",
+    "sizes": "16x16",
+    "type": "image/png"
+  },
+  {
+    "src": "favicon-32x32.png",
+    "sizes": "32x32",
+    "type": "image/png"
+  }]
+}

static/sw.js

@@ -0,0 +1 @@
+self.addEventListener('fetch', (event) => {});

themes/hello-friend-ng/layouts/partials/head.html

@@ -6,6 +6,12 @@
 <meta name="keywords" content="{{ .Site.Params.keywords }}" />
 <meta name="robots" content="noodp" />
 <link rel="canonical" href="{{ .Permalink }}" />
+<script>
+if ('serviceWorker' in navigator) {
+  // sw.js can literally be empty, but must exist
+  navigator.serviceWorker.register('/sw.js');
+}
+</script>
 
 {{ block "title" . }}
 <title>
@@ -23,6 +29,10 @@
 <!-- JS -->
 <script src="https://assets.digitalclimatestrike.net/widget.js" async></script>
 
+<!-- PWA -->
+<link rel="manifest" href="manifest.webmanifest" />
+<script src="https://cdn.jsdelivr.net/npm/pwacompat@2.0.9/pwacompat.min.js" integrity="sha384-VcI6S+HIsE80FVM1jgbd6WDFhzKYA0PecD/LcIyMQpT4fMJdijBh0I7Iblaacawc" crossorigin="anonymous" async></script>
+
 {{ $options := (dict "targetPath" "main.css" "outputStyle" "compressed" "enableSourceMap" true) }}
 {{ $style := resources.Get "scss/main.scss" | resources.ToCSS $options | resources.Minify | resources.Fingerprint }}
 <link rel="stylesheet" href="{{ $style.RelPermalink }}">