build(blaze-elements): add index with re-exported elements

[elmariofredo]

I'm submitting a ... (check one with "x")

[ ] bug report => search github for a similar issue or PR before submitting
[x] feature request
[ ] support request => You can submit support request here, but we preffer to chat about it realtime at our [ngParty slack](https://ngparty.herokuapp.com/)

Current behavior
we are not reexporting dependant packages as in https://github.com/material-components/material-components-web/blob/master/packages/material-components-web/index.js

Expected behavior
we should add reexporting index