add escape sequence interpretations for OSC strings

[ChrisAshworth]

I believe that currently we do not process escape characters inside OSC strings when they are specified via the "QSC" human-compatible text. So, for example, if someone provides the following string to messageWithString::

/cue/my/message "a string where I want \n a newline"

It will generate an OSC message with a string argument that contains \n rather than an ASCII newline character.

I think we should probably process some escape sequences inside string arguments. Maybe these:

• \n : new line
• \r : carriage return
• \t : horizontal tab
• \v : vertical tab
• \f : form feed / new page

I think we'd change this somewhere around here:

https://github.com/Figure53/F53OSC/blob/main/Sources/F53OSC/F53OSCMessage.m#L238