update TODO

TODO.md

@@ -8,10 +8,12 @@ Performance:
 * update cells should only update the changed cells
 * for scrollback, investigate using segmented list for sufficiently large
   scrollback scenarios.
+* scrollback: dynamic growth rather than prealloc
 
 Correctness:
 
 * `exit` in the shell should close the window
+* scrollback: reflow on resize
 * test wrap against wraptest: https://github.com/mattiase/wraptest
   - automate this in some way
 
@@ -19,9 +21,12 @@ Visual:
 
 * bell
 
+Improvements:
+
+* scrollback: configurable
+
 Major Features:
 
-* History, mouse scrolling
 * Line wrap
 * Selection, highlighting
 * Copy (paste is done)