Correctly indent splicing reader conditionals

[mrichards42]

Adjusts is_reader_conditional_special_case to also match splices, i.e. #?@. The test case is taken from https://clojure.org/guides/reader_conditionals

Without this, splicing conditionals are indented as functions, e.g.

 #?@(:clj  [5 6 7 8]
           :cljs [1 2 3 4])))

[axvr]

Thanks! Tested and merged.