Use productName from package.json (#2580)

Signed-off-by: Jari Kolehmainen <jari.kolehmainen@gmail.com>

src/renderer/template.html

@@ -2,11 +2,11 @@
 <html lang="en">
 <head>
   <meta charset="UTF-8">
-  <title>Lens - The Kubernetes IDE</title>
+  <title>OpenLens - Open Source Kubernetes IDE</title>
 </head>
 <body>
 
 <div id="app"></div>
 
 </body>
-</html>
+</html>