jank support

Hey Bruce. 🙂 rebel-readline is badass and it's the exact sort of *default experience* I want [jank](https://github.com/jank-lang/jank) users to have. We'll have a lot of native devs new to Clojure, without proper REPL clients set up, and I want that experience to still be polished. So, I see that rebel-readline is based on JLine, which would not be available within C++. Based on perusing the source, and keeping a mental tally of the interop, my gut says that forking this to rip out the Java bits and replace them with C++ bits is going to be a lot of work. I wanted to get your read on this, though. jank is already using [ftxui](https://github.com/ArthurSonzogni/FTXUI) for its error reporting, so we could definitely cook up a rebel-readline-like system, but the ideal would be strong compatibility with the config and feature parity. I'm not interested in having something jank-specific, since nobody wins with that. If we do build our own, the features we do implement should follow rebel-readline so that the same config can be used, even if jank ignores keys for features it doesn't yet support. I'd appreciate your thoughts on this, in particular how feasible it would be to maintain a fork with JLine and the rest of the Java interop ripped out and replaced with separate C++ libs.