Enhancement: Better error reporting on invalid config files

[manthanabc]

Improves error reporting when config parsing related errors
This along with this pr will allows pest error to be visible when config file parsing fails

Current Output

thread 'main' panicked at swhkd/src/config.rs:7:80:
called `Result::unwrap()` on an `Err` value: Grammar(Error { variant: ParsingError { positives: [command], negatives: [] }, location: Pos(9), line_col: Pos((1, 10)), path: Some("/home/manth/swhkdrc"), line: "super + a; f ", continued_line: None, parse_attempts: None })
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

New output

[2025-01-11T20:39:07Z ERROR swhkd] Config Error: unable to parse config file

New output after sweet with this pr

[2025-01-11T20:42:57Z ERROR swhkd] Config Error:
     --> /home/manth/swhkdrc:1:10
      |
    1 | super + a; f
      |          ^---
      |
      = expected command
    Unable to parse config file

for reference #287

[manthanabc]

closing in favor of #289