The previous version of the GB-18030 standard was published in 2005.
This commit adds support for the updated (2022) version of this text
encoding. The existing GB18030 implementation has been left unchanged
for backwards compatibility; users who want to use the new standard
must explicitly indicate the desired text encoding is 'GB18030-2022'.
The document which defines GB18030-2022, published by the government
of the People's Republic of China, defines three levels of standards
compliance. This implementation is intended to achieve Implementation
Level 3, which is the highest level of compliance.
Experts in the GB18030 standard are requested to assess this
implementation and report any deviation from the standard.
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