Base-CJK

Use CJK characters to encode to binary data to text.

CJK chracter ranges:

CJK Unified Ideographs	4E00-9FFF	Common
CJK Unified Ideographs Extension A	3400-4DBF	Rare

This utility converts every 13 bits to a Unicode code point which lies in the range of `[4E00, 6E00)`. In addition, 8E00 is also used as a functional character to show whether the ending byte is split to 2 code points or not. In v1, in order to support streaming mode, we make `[6E00, 7E00)` in use, which has 2^12 code points, to indicate the end of file without introducing control characters with no information, which requires the decoder to peek 1 character forward while somehow impossible in streaming.