v2.0.0 of dart_dash_otp

Generate and verify TOTP and HOTP one-time passwords (RFC 6238 / RFC 4226) for 2FA and MFA, with otpauth:// URIs compatible with Google Authenticator. Changelog excerpt: Major rewrite. Contains breaking changes. ### Breaking changes - Dart SDK constraint bumped to >=3.0.0 <4.0.0. - OTP.digits, OTP.secretand OTP.algorithmare now final. - TOTP.intervalis now a non-nullable final int; constructors validate that it is positive. - Generated otpauth://URLs now use the Google Authenticator Issuer:Accountlabel format instead of just Account. - All query parameters in the generated URL are URL-encoded. - Util.intToBytelist's paddingparameter was[...]