Add Babashka support

[matthewdowney]

I'm opening this PR to track progress, but it's not quite ready to merge yet.

So far we have

• Support for running ;=> assertions from Babashka, albeit without file names / numbers.
• Support for a subset of ;=>> assertions (mirroring whatever matcho supports out of the box).

[matthewdowney]

More examples here of what works and what doesnt:

rich-comment-tests/bb/test_rct_with_bb.bb

Lines 9 to 45 in 2888610

	(deftest rct-tests
	(testing "simple assertions"
	(t/passes? "(range 3) ;=> (0 1 2)")
	(t/fails? "(range 3) ;=> (0 2 2)" "actual: (not (= (0 1 2) (0 2 2)))")
	(t/passes?
	"(+ 5 5)
	; => 10")
	(t/fails?
	"; 5 times 5
	(* 5 5) ;=> 35"
	"; 5 times 5" ; includes the context
	"actual: (not (= 25 35))"))
	(testing "reflective tests"
	(testing "when evaluating a :rct/test comment form in a .bb file"
	(let [ns-tests-result
	(binding [test/*report-counters* (atom test/*initial-report-counters*)]
	(rct/run-ns-tests! 'test-rct-with-bb))]
	(is (= ns-tests-result {:test 1 :pass 4 :fail 0 :error 0})
	"tests passing"))))
	(testing "compatible subset of matcho assertions"
	(t/passes? "(+ 5 5) ;;=>> int?")
	(t/fails? "(+ 5 5) ;;=>> string?" "Matcho pattern mismatch:"))
	;; TODO: Figure out how to make these pass :)
	#_(testing "(still) incompatible subset of matcho assertions"
	(t/passes? "(range 3) ;;=>> '(0 1 2)")
	(t/passes? "(assoc {} :foo :bar :bar :baz) ;;=>> {:foo :bar ...}")
	(t/passes? "(+ 5 5) ;=>> 10"))
	#_(testing "includes file names and line numbers in assertions"
	(is (str/starts-with? (t/rct "(+ 1 1) ;=> 3")
	"\nFAIL in () (rct_babashka_test.bb:2)\n"))))

• Files and line numbers in Babashka are probably possible, I bet I'm doing something wrong with SCI
• Matcho does not totally run on Babashka as-is, even though it should because spec is supported. I suspect this would be easy to address, but would require forking the project or getting a PR merged.
• Malli runs on Babashka, and could supplant Matcho, but I like how Matcho allows literal syntax for map comparisons, not just spec.

[matthewdowney]

Ok turns out missing file and line numbers are due to babashka/babashka#1451

[matthewdowney]

Now all that's missing is Matcho, described here: HealthSamurai/matcho#7

It's a small enough codebase that I can always just fork it.

[matthewdowney]

Ok so this is complete, pending file names and line numbers in Babashka, which will work as of the next release, at which time I'll uncomment the following test:

rich-comment-tests/bb/test_rct_with_bb.bb

Lines 41 to 43 in e799269

	#_(testing "includes file names and line numbers in assertions"
	(is (str/starts-with? (t/rct "(+ 1 1) ;=> 3")
	"\nFAIL in () (rct_babashka_test.bb:2)\n"))))