textproc/rubygem-yarp: Add rubygem-yarp 0.6.0

Yet Another Ruby Parser is a parser for the Ruby programming language. It is
designed to be portable, error tolerant, and maintainable. It is written in C99
and has no dependencies. It is currently being integrated into CRuby, JRuby,
TruffleRuby, Sorbet, and Syntax Tree.