Position of RBS::Location should be byte length

I'm developing a tool using RBS.
And I'm trying to load RBS files using RBS::MethodType#location and display them with colors.

During development, a problem occurred where the display is off by one character only in core/math.rbs.

In core/math.rbs, the character π is used in the documentation, which is a 2 byte character.

Upon investigation, it appears that the positions in Location are recorded not in byte size but in the number of UTF-8 characters.

# Whether the comment is `π` or `p`, the class location has not changed.

::RBS::Parser.parse_signature("#π\nclass Foo\nend")[2][0].location.start_pos
#=> 3
::RBS::Parser.parse_signature("#p\nclass Foo\nend")[2][0].location.start_pos
#=> 3

Recording the position in bytesize would make it more convenient for reading with methods like IO#read, so I believe it should be recorded in bytesize.

What do you think?

Start with RBS::Location and the positions returned by RBS::Parser.parse_signature, using the core/math.rbs example with π as the reproduction case. Check how location offsets are consumed with IO#read; done means positions account for UTF-8 byte length and the π/p comparison behaves as intended.