Improve grammar in TODO description

Author: realityforge

TODO.md

@@ -1,6 +1,6 @@
 # TODO
 
-This document is essentially a list of shorthand notes describing work yet to completed.
+This document is essentially a list of shorthand notes describing work yet to be completed.
 Unfortunately it is not complete enough for other people to pick work off the list and
 complete as there is too much un-said.