v0.0.1 of genotp_flutter

TOTP/HOTP one-time password plugin for Flutter, powered by genotp-go via gomobile. Works on Android and iOS with no network dependency. Changelog excerpt: Initial release. - TOTP generation and verification via GenotpFlutter.generateTotp/ verifyTotp - HOTP generation via GenotpFlutter.generateHotp - Secret generation via GenotpFlutter.generateSecret - otpauth://URI builder for QR code display - Android (API 24+) and iOS (13+) support - Backed by genotp-govia gomobile