better error messages that return what line and what column the problem is at

[jestarray]

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Message("invalid type: cons cell, expected a number", None)', src\main.rs:778:59

I have no idea where this is at.

[rotty]

serde-lexpr should probably play the same shenanigans as serde_json does, which has extra code to round-trip the location information by parsing the string produced by the error's Display implementation.