Support Reline.dump to help investigate issues

[st0012]

Description

When an input issue happens, users could type Reline.dump, and it will

1. Collect important states (TBD)
2. Serialises it to an easily-comparable format (json or yaml?)
3. Dump the data to a pre-defined file path (so users won't need to copy it from a messed up output)

This will be similar to irb_info in IRB that should help us collect helpful information before we look into the issue, and speed up the investigation.