dowlnoad link on about page

Frontend/patient_manager/web/index.html

@@ -96,6 +96,7 @@
       document.body.style.background = "transparent";
     }
   </script>
+  <script src="install_pwa.js" defer></script>
   <!-- Splash screen -->
   <!-- <script>
     var dartPdfJsBaseUrl = "https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.2.146/";