add PieceTable::begin_insert()

src/gui/Window.cc

@@ -274,6 +274,9 @@ void Window::handle_key(uint32_t scancode, uint32_t mod)
         m_buffer->piece_table->undo();
         redraw();
         break;
+    case SDL_SCANCODE_I:
+        m_buffer->piece_table->begin_insert(*m_cursor, true);
+        break;
     }
 }