♿ improved parse error messages

doc/examples/parse_error.output

@@ -1,3 +1,3 @@
-message: [json.exception.parse_error.101] parse error at line 1, column 8: syntax error - unexpected ']'; expected '[', '{', or a literal
+message: [json.exception.parse_error.101] parse error at line 1, column 8: syntax error while parsing value - unexpected ']'; expected '[', '{', or a literal
 exception id: 101
 byte position of error: 8