[Sharing is Caring] Move `truffle-assertions` typings upstream.

[nlordell]

They can either be moved to be part of the truffle-assertions project directly or part of the @types organization.

They are relatively simple typings here: https://github.com/gnosis/dex-contracts/blob/master/types/truffle-assertions/index.d.ts

[bh2smith]

I'm not sure I understand the goal here. Are we to move the content of the file linked in the description to a different repo? Like truffle-assertions?

[nlordell]

Turns out its a little more complicated - there are some type dependencies that need to be setup correctly.