CodePage constructor
Creates a code page with the given name and characters.
The characters
string must contain 256 code points (runes)
in the order of the bytes representing them.
Any byte not defined by the code page should have a
U+FFFD (invalid character) code point at its place in
characters
.
The name is used by Encoding.name.
Implementation
factory CodePage(String name, String characters) = CodePage._general;