More TODOs

TODO.md

@@ -7,3 +7,6 @@ Global parameters to control encoder settings:
   - Linear term
 - Number of quants to keep, per tile.
 - Whether to use wide or packed representation for the thumbnail block
+Interleave layers instead of having them consecutively.
+Maybe have a second instance of the global parameters block for the alpha channel.
+Actually support terminating early for "progressive" loads