Update to-do.md

to-do.md

@@ -2,6 +2,7 @@
 2. patent acceptance prediction
 3. predict the primary IPC or CPC code of a patent application given (some subset of) the text of the application.
 4. abstractive summarization: given the claims or claims section of a patent application, generate the abstract.
+5. chatwPatent
 
 
 dataset--