The first byte could be one of the following. The X indicates bits available to encode the character.
0XXXXXXX only one byte 0..0x7F (ASCII)
All following bytes have the format: 10XXXXXX
The index for the character is right-aligned in the combined X bits.
110XXXXX two bytes Max char value is 0x7FF
1110XXXX three bytes Max char value is 0xFFFF
11110XXX four bytes Max char value is 0x1FFFFF
111110XX five bytes Max char value is 0x3FFFFFF
1111110X six bytes Max char value is 0x7FFFFFFF