convert_hex 0.2.0

Hexadecimal conversion for easier adjustment

0.2.0 Support null safety.

• Edit class Hex to ConvertHex
• use function convertHex

0.1.7 Fix Base 16

• Fix function Hex charDecode and charEncode

0.1.6 Fix Base 64

• Edit how to use hex64
• Add return StatusEncode in encode Hex64

0.1.5 Add Base

• Add Convert Hex64

0.1.0 Base Hex

• Convert Hex