1.2.0

feat: add Big5Encoder (Unicode→Big5), bump to 1.2.0

- Big5Encoder mirrors Big5Decoder via a lazy reverse lookup over the
  existing mapping table; encode() throws on unmapped chars, encodeLossy()
  skips them.
- Round-trip + known-byte + ASCII tests.

1.1.1

• Optimize package with pana recommendations

1.1.0

• Remove dart:io dependency to improve portability

1.0.0

• First Release