Add "U" template to doc
@@ -38,6 +38,7 @@ There is no dependency on other mrbgems.
- q : 64-bit signed, native endian (`int64_t`)
- S : 16-bit unsigned, native endian (`uint16_t`)
- s : 16-bit signed, native endian (`int16_t`)
+ - U : UTF-8 character
- V : 32-bit unsigned, VAX (little-endian) byte order
- v : 16-bit unsigned, VAX (little-endian) byte order
- x : null byte
