WIP add support for Babashka

[AndreTheHunter]

Summary

https://github.com/l3nz/cli-matic/issues/113

• added :bb specific reader conditionals
• made expound an optional dependency
• made cljc.java-time a required dependency
• combined optionals.clj and .cljs into .cljc
• combined platform.clj and .cljs into .cljc
• created bb-test.sh and bb_runner.cljc for running tests in Babashka
• a lot of simplification and cleanup

TODO

Outstanding changes are marked as FIXME

• [ ] update Babashka to support missing features https://github.com/l3nz/cli-matic/pull/128
• [ ] fix cljs tests (currently failing on `master)
• [ ] fix clj yaml test (currently failing on `master)
• [ ] fix clj spec test
• [ ] test installed artifact (compiled .jar) in Babashka
• [ ] add yaml support
• [ ] add usage example
• [ ] update Readme

[AndreTheHunter]

Phew, that was quite the rampage. Happy to answer any questions or discuss any changes/improvements. Feel free to jump in since "Allow edits and access to secrets by maintainers" is on. @l3nz

[l3nz]

Sorry I clicked on wrong button. :-)

Couple of comments:

• I would not want a conditional for fdef, it is really polluting the code. Can we somehow inject a dummy do-nothing fdef into the spec, maybe with a conditional?
• IIRC, I think that expound is used somewhere to generate error messages
• what are things that need upstream (bb) support? I'd rather ship a feture less than depend on very latest

In general, good job! very torough. Having bb would be major (and being included in bb even more :-) )

[l3nz]

Closing because of #145