docs: Add MDL migration guide.
docs: Add MDL migration guide.

Implements #130.
[skip ci]

pgbross/material-components-web,material-components/material-components-web,Yizhachok/material-components-web,material-components/material-components-web,pgbross/material-components-web,Yizhachok/material-components-web,anton-kachurin/material-components-web,material-components/material-components-web,anton-kachurin/material-components-web