Add ListingDetails helper class

helpers/listing-page.js

@@ -0,0 +1,32 @@
+
+
+import {
+    getAppType
+} from './app-derived.js'
+
+
+export class ListingDetails {
+    constructor ( listing ) {
+        this.listing = listing
+
+        this.type = getAppType( listing )
+    }
+
+    type = ''
+
+    get mainHeading () {
+        if ( this.type === 'formula' ) {
+            return `Does <code>${ this.listing.name }</code> work on Apple Silicon when installed via Homebrew?`
+        }
+
+        return `Does ${ this.listing.name } work on Apple Silicon?`
+    }
+
+    get subtitle () {
+        return this.listing.text
+    }
+
+    buildListingDetails ( listing ) {
+
+    }
+}