Add initial implementation of Docker Compose manager and example usage

- Introduced DockerComposeManager class for programmatically creating and managing Docker Compose YAML files.
- Added example script demonstrating usage of DockerComposeManager.
- Created tests for service creation, modification, and removal.
- Included project metadata in pyproject.toml and added linting instructions in copilot-instructions.md.

tests/test_compose_manager.py

@@ -0,0 +1,62 @@
+from pathlib import Path
+
+import pytest
+import yaml
+
+from compose import DockerComposeManager
+
+
+def test_create_and_save_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    manager.create_service(
+        name="web",
+        image="nginx:latest",
+        ports=["80:80"],
+        environment={"ENV_VAR": "value"},
+    ).save()
+    # Check file exists and content
+    assert compose_file.exists()
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert "web" in data["services"]
+    assert data["services"]["web"]["image"] == "nginx:latest"
+    assert data["services"]["web"]["ports"] == ["80:80"]
+    assert data["services"]["web"]["environment"] == {"ENV_VAR": "value"}
+
+
+def test_modify_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    manager.create_service(name="web", image="nginx:latest").save()
+    manager.modify_service(name="web", image="nginx:1.19", ports=["8080:80"]).save()
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert data["services"]["web"]["image"] == "nginx:1.19"
+    assert data["services"]["web"]["ports"] == ["8080:80"]
+
+
+def test_remove_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    manager.create_service(name="web", image="nginx:latest").save()
+    manager.remove_service("web").save()
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert "web" not in data["services"]
+
+
+def test_context_manager(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    with DockerComposeManager(str(compose_file)) as manager:
+        manager.create_service(name="web", image="nginx:latest")
+    with compose_file.open() as f:
+        data = yaml.safe_load(f)
+    assert "web" in data["services"]
+
+
+def test_modify_nonexistent_service(tmp_path: Path) -> None:
+    compose_file: Path = tmp_path / "docker-compose.yml"
+    manager = DockerComposeManager(str(compose_file))
+    with pytest.raises(KeyError):
+        manager.modify_service("notfound", image="nginx:latest")