[FEATURE] Export parse method for call outside libary.

[gapkukb]

Is your feature request related to a problem? Please describe.

Sometimes we are unneccessay to scan a qrcode by camera , just upload the image file by user and detect the qrcode .

Describe the solution you'd like

The libary can export a parse function just only to parse the qrcode image from disk or user uploaded image. but now inside the libary is a private method cannnot call it at outside . for excample . the file located "lib/src/web/flutter_qr_web.dart" , there is a method named "_captureFrame2" , consider move the method as a static method on WebQrView,or add a parse method on the QEViewController, then developer can call it anywhere if is needed.

Thank you.

Additional context
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