Prefetch external assets for caching

ngsw-config.json

@@ -13,7 +13,14 @@
       "installMode": "lazy",
       "updateMode": "prefetch",
       "resources": {
-        "files": ["/assets/**"],
+        "files": ["/assets/**"]
+      }
+    },
+    {
+      "name": "external assets",
+      "installMode": "prefetch",
+      "updateMode": "prefetch",
+      "resources": {
         "urls": [
           "https://firebasestorage.googleapis.com/v0/b/fhsons-7e90b.appspot.com/o/**",
           "https://use.fontawesome.com/releases/v5.1.0/css/all.css",

src/app/about/about.component.html

@@ -1,7 +1,7 @@
 <div class="container">
   <div class="row">
     <div class="col-12 py-4">
-      <img src="http://via.placeholder.com/350x250" class="float-left img-fluid mb-4 mr-4">
+      <img src="https://via.placeholder.com/350x250" class="float-left img-fluid mb-4 mr-4">
       <h2 class="mb-4 roboto">40 Years of Excellence</h2>
       <hr class="ml-4" />
       <strong>FH &amp; Sons</strong> has been in business for 40 years. We have been ISO 9001:2000 certified since May 2000. Our