**Problem:** Parsing can be slow for large files, and it is a blocking
operation which can be disruptive and annoying.
**Solution:** Provide a function for asynchronous parsing, which accepts
a callback to be run after parsing completes.
Co-authored-by: Lewis Russell <lewis6991@gmail.com>
Co-authored-by: Luuk van Baal <luukvbaal@gmail.com>
Co-authored-by: VanaIgr <vanaigranov@gmail.com>