Add JSON reporter (#2706)

Co-authored-by: Martin Hořeňovský <martin.horenovsky@gmail.com>

src/catch2/catch_all.hpp

@@ -74,6 +74,7 @@
 #include <catch2/internal/catch_getenv.hpp>
 #include <catch2/internal/catch_is_permutation.hpp>
 #include <catch2/internal/catch_istream.hpp>
+#include <catch2/internal/catch_jsonwriter.hpp>
 #include <catch2/internal/catch_lazy_expr.hpp>
 #include <catch2/internal/catch_leak_detector.hpp>
 #include <catch2/internal/catch_list.hpp>