add copy formatter

PyTeX/format/copy_formatter.py

@@ -0,0 +1,18 @@
+from .formatting_config import FormattingConfig
+from .pytex_formatter import PyTeXFormatter
+from pathlib import Path
+import shutil
+
+from typing import List, Tuple
+
+
+class CopyFormatter(PyTeXFormatter):
+    def output_files(self) -> List[str]:
+        return [self.input_file.name]
+
+    def format(self, build_dir: Path, overwrite: bool = False) -> List[Tuple[str, FormattingConfig]]:
+        shutil.copy(self.input_file, build_dir / self.input_file.name)
+        return []
+
+    def dependencies(self) -> List[str]:
+        return []  # TODO