feat: add builds module for saving and reusing configurations

- Add Build struct with TOML serialization
- Implement build list/save/delete commands
- Store builds in ~/.gitkit/builds/
- Add capture_current_config to detect current repo state
- Add detect_gitignore_templates and detect_gitattributes_presets

Author: JheisonMB

Cargo.toml

@@ -15,6 +15,8 @@ path = "src/main.rs"
 [dependencies]
 anyhow = "1"
 clap = { version = "4", features = ["derive"] }
+serde = { version = "1", features = ["derive"] }
+toml = "0.8"
 ureq = "2"
 
 [dev-dependencies]