added basic PWA functionality

public/index.html

@@ -5,6 +5,7 @@
     <meta http-equiv="X-UA-Compatible" content="IE=edge">
     <meta name="viewport" content="width=device-width">
     <link rel="icon" href="<%= BASE_URL %>favicon.ico">
+    <link rel="manifest" href="<%= BASE_URL %>manifest.json" />
     <title><%= htmlWebpackPlugin.options.title %>  - Der Datensparsame Verhaltenstest</title>
     <meta name="description" content="Die COVID-19 Verhaltensdiagnose, die keine Daten speichert." />
     <meta name="keywords" content="corona, coronavirus, covid19, covid-19, wirvsvirus, wir-vs-virus, covid19test, covidtest, coronatest, corona-test" />

public/manifest.json

@@ -0,0 +1,10 @@
+{
+  "name": "COVIDassist",
+  "short_name": "COVIDassist",
+  "icons": [],
+  "start_url": "./index.html",
+  "display": "standalone",
+  "scope": "/",
+  "background_color": "#FCF7F8",
+  "theme_color": "#FCF7F8"
+}