将docling设为动态导入

docutranslate/converter/__init__.py

@@ -1,3 +1,6 @@
 from .converter import Document,Converter
 from .converter_mineru import ConverterMineru
-from .converter_docling import ConverterDocling
+
+from docutranslate.global_values import  conditional_import
+if conditional_import("docling"):
+    from .converter_docling import ConverterDocling