feat!: Account features

- Bump version to 0.2.0
- Added trait SquadObject
- Implemented SquadObject for Quest and Account
- Implemented Config::load_accounts
- Removed src/quest/error.rs
- Added account tests in tests/main.rs

BREAKING CHANGE: Quest::{load,delete,save} are now provided by
SquadObject trait

tests/io.rs

@@ -1,4 +1,4 @@
-use squad_quest::{config::Config,error::Error,quest::Quest};
+use squad_quest::{SquadObject, config::Config, error::Error, quest::Quest};
 use std::path::PathBuf;
 
 const CONFIG_PATH: &str = "tests/io/config.toml";