v3.1.0

[3.1.0] - 2026-06-20

Added

• Alphanumeric CNPJ support (in effect from July 2026): the 12-character base may
  now contain the letters A-Z in addition to digits, followed by 2 numeric
  check digits. Each character contributes its value as ASCII − '0' (digits map
  to 0-9, letters to 17-42) using the same mod-11 algorithm as numeric CNPJ.
• CNPJ.GenerateAlphanumeric() generates a random valid alphanumeric CNPJ.
• digit.RemoveCNPJFormatting strips CNPJ formatting (dots, dashes, slashes,
  whitespace) and upper-cases the result while preserving letters.
• digit.GenerateAlphanumericChars generates random alphanumeric characters
  (0-9, A-Z).

Changed

• CNPJ.IsValid and CNPJ.Format now accept both numeric (legacy) and
  alphanumeric CNPJs. Input is sanitized with RemoveCNPJFormatting (which keeps
  letters) instead of RemoveNonDigits. As a result, a 14-character input that
  contains letters and matches the alphanumeric shape but fails the checksum now
  returns ErrCNPJInvalid rather than ErrCNPJInvalidLength.