add visit to parser exports

Author: tintinweb

solidity_parser/__init__.py

@@ -1,2 +1,3 @@
-from .parser import parse_file, parse, objectify
-__ALL__ = ["parse","parse_file","objectify"]
+from .parser import parse_file, parse, objectify, visit
+
+__ALL__ = ["parse", "parse_file", "objectify", "visit"]