wip: use stateful buffer

packages/autofmt/src/buffer.rs

@@ -0,0 +1,17 @@
+use std::fmt::Result;
+
+struct Buffer {
+    buf: String,
+    cur_line: usize,
+    cur_indent: usize,
+}
+
+impl Buffer {
+    fn write_tabs(&mut self, num: usize) -> Result {
+        todo!()
+    }
+
+    fn new_line(&mut self) -> Result {
+        todo!()
+    }
+}