Optimization intro.md (#666)
Optimization intro.md (#666)

* intro

* intro initial

* intro 1st done

* rename

* delete intro
d2l-ai/d2l-zh,d2l-ai/d2l-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,mli/gluon-tutorials-zh,d2l-ai/d2l-zh