Revert "Revert "add ptb data""
Revert "Revert "add ptb data""

This reverts commit b9a1cc45b76bb67ec5088865e39bc44cbc116325.

d2l-ai/d2l-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,d2l-ai/d2l-zh,d2l-ai/d2l-zh,mli/gluon-tutorials-zh