重构代码，新增了MarkdownBasedManager和TXTManager实现

docutranslate/ir/document.py

@@ -0,0 +1,24 @@
+import dataclasses
+from pathlib import Path
+
+class Document:
+    def __init__(self,suffix:str,content:bytes,stem:str|None=None,path:Path=None):
+        self.suffix=suffix
+        self.content=content
+        self.stem=stem
+        self.path=path
+    @property
+    def name(self)->str|None:
+        if not self.stem:
+            return None
+        return self.stem+self.suffix
+
+    @classmethod
+    def from_path(cls,path:Path|str):
+        if isinstance(path,str):
+            path=Path(path)
+        return cls(suffix=path.suffix,content=path.read_bytes(),stem=path.stem,path=path)
+
+    @classmethod
+    def from_bytes(cls,content:bytes,suffix:str,stem:str|None):
+        return cls(content=content,suffix=suffix,stem=stem)

docutranslate/ir/markdown_document.py

@@ -0,0 +1,7 @@
+from docutranslate.ir.document import Document
+
+
+class MarkdownDocument(Document):
+    def __init__(self,*args,**kwargs):
+        super().__init__(*args,**kwargs)
+        self.suffix=".md"