frontend: Add manifest.json for better mobile experience

Also added a meta description and an apple-touch-icon that will be displayed
on iOS devices as icon. This makes it possible to use the webapp a bit
like a native app. A serviceworker is not in use yet, since the app does
not really work well offline...

frontend/angular.json

@@ -28,6 +28,7 @@
             "aot": true,
             "assets": [
               "src/favicon.ico",
+              "src/manifest.json",
               "src/assets"
             ],
             "styles": [

frontend/src/index.html

@@ -5,7 +5,10 @@
   <title>OpenEnergize</title>
   <base href="/">
   <meta name="viewport" content="width=device-width, initial-scale=1">
+  <meta name="description" content="Open Source Energy management platform">
   <link rel="icon" type="image/x-icon" href="favicon.ico">
+  <link rel="manifest" href="manifest.json">
+  <link rel="apple-touch-icon" href="/assets/touch-icon-192.png">
   <link rel="preconnect" href="https://fonts.gstatic.com">
   <link href="https://fonts.googleapis.com/css2?family=Roboto:wght@300;400;500&display=swap" rel="stylesheet">
   <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">

frontend/src/manifest.json

@@ -0,0 +1,22 @@
+{
+  "name": "OpenEnergize",
+  "short_name": "OpenEnergize",
+  "start_url": "/",
+  "scope": "/",
+  "display": "standalone",
+  "background_color": "#3f51b5",
+  "theme_color": "#3f51b5",
+  "description": "An open source energy management platform",
+  "icons": [
+    {
+      "src": "/assets/touch-icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "/assets/touch-icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png"
+    }
+  ]
+}