Rust 1.85.0 + Rust 2024 Edition (#68)

- Add `rust-toolchain.toml`
- Refactor `flake` to consider `rust-toolchain.toml`, especially Rust version
- `just`: Add run-sound command
- Ignore sound files
- Format

src/config.rs

@@ -1,5 +1,5 @@
 use crate::constants::APP_NAME;
-use color_eyre::eyre::{eyre, Result};
+use color_eyre::eyre::{Result, eyre};
 use directories::ProjectDirs;
 use std::fs;
 use std::path::PathBuf;