refactor: rename 'database.db' to 'db.sqlite3'

Author: ShenMian

Diff for: .gitignore

@@ -4,4 +4,4 @@
 /.idea
 config.toml
 keymap.toml
-database.db
+db.sqlite3

Diff for: src/systems/level.rs

@@ -16,7 +16,7 @@ use std::sync::Mutex;
 
 /// Sets up the database, initializes it, and loads levels from files into the database.
 pub fn setup_database(mut commands: Commands) {
-    let database = database::Database::from_file(Path::new("database.db"));
+    let database = database::Database::from_file(Path::new("db.sqlite3"));
     database.initialize();
     info!("Loading levels from files");
     for path in fs::read_dir("assets/levels/").unwrap() {