chapter_recurrent-modern/bi-rnn (#726)
chapter_recurrent-modern/bi-rnn (#726)

* chapter_recurrent-modern/bi-rnn

* Update bi-rnn.md

Co-authored-by: goldmermaid <fcb00cecbf879d17a80f4ce26a389eda39da7621@berkeley.edu>
d2l-ai/d2l-zh,mli/gluon-tutorials-zh,d2l-ai/d2l-zh,mli/gluon-tutorials-zh,d2l-ai/d2l-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh