fix: Specify UTF8 encoding for output

Issue-26: #26

Author: pawamoy

src/griffe2md/_internal/main.py

@@ -18,7 +18,7 @@
 
 def _output(text: str, to: IO | str | None = None) -> None:
     if isinstance(to, str):
-        with Path(to).open("w") as output:
+        with Path(to).open("w", encoding="utf8") as output:
             output.write(text)
     else:
         if to is None: