Support syntax highlighting

In 2017 the project https://github.com/gohxs/readline forked off this in order to provide syntax highlighting capabilities. That capability is the reason why some projects still depend on it, for example [usql](https://github.com/xo/usql/pull/535#issuecomment-3120838982). According to https://github.com/chzyer/readline/pull/116 the syntax highlighting capability was merged into this version. Is anyone using it? Is it supposed to work? In a quick test by @kenshaw this `chzyer/readline` does not seem to support syntax highlighting.