Expose some Rope functions through TextBuffer

This is mostly just to silence unused code warnings for now.

core/src/text_buffer/mod.rs

@@ -2,6 +2,7 @@ use std::rc::Rc;
 
 mod rope;
 use rope::Rope;
+pub use rope::{CharIterator, CharWithPointIterator};
 
 pub struct TextBuffer {
     contents: Rc<Rope>,
@@ -53,6 +54,18 @@ impl TextBuffer {
             }
         }
     }
+
+    pub fn delete_at_char_index(&mut self, start: usize, length: usize) {
+        self.contents = self.contents.delete_at_char_index(start, length)
+    }
+
+    pub fn iter_chars(&self) -> CharIterator {
+        self.contents.iter_chars()
+    }
+
+    pub fn iter_chars_with_point(&self) -> CharWithPointIterator {
+        self.contents.iter_chars_with_point()
+    }
 }
 
 impl Default for TextBuffer {