feat: Async api (#60)

Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>

docling_serve/settings.py

@@ -3,6 +3,8 @@ from typing import Optional, Union
 
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
+from docling_serve.datamodel.engines import AsyncEngine
+
 
 class UvicornSettings(BaseSettings):
     model_config = SettingsConfigDict(
@@ -28,6 +30,9 @@ class DoclingServeSettings(BaseSettings):
     enable_ui: bool = False
     artifacts_path: Optional[Path] = None
 
+    eng_kind: AsyncEngine = AsyncEngine.LOCAL
+    eng_loc_num_workers: int = 2
+
 
 uvicorn_settings = UvicornSettings()
 docling_serve_settings = DoclingServeSettings()