Is there any possible way to put a QR reader on the website and when the website is open on android mobile browser there would be an icon for the QR Reader and when it tapped it will open the QR Reader? I've seen like airdroid app and you want to access airdroid on web you just have to scan the QR Code on the web via airdroid app. I was thinking if this can be done without creating an app to read a QR Code
you can use this to read qr codes https://webqr.com/. not sure how you are gonna get data back to your website.
If thats happens to be a trouble you can access its source code here https://github.com/LazarSoft/jsqrcode and modify it to your requirements