Feature/906 add dfyn dex

[jorgedclopes]

Summary

Fixes #906
Adds DFYN to the routing options when swapping.

Image - On localhost

Background

In order to add more options/value to our platform, we want to add more relevant dexes to the list of swap options.

To Test/Replicate

1. Follow the procedure to link the SDK locally (see below)
2. yarn build
3. Change network to Polygon
4. Select compatible token pair.

IMPORTANT

This PR uses unreleased SDK.

TL;DR
To make it work you need to build & link this SDK branch locally.

How to do that: (from relevant PR)

Clone SDK repo locally
Checkout to feature/add-polygon-config on the SDK repo
run yarn prepublishOnly
run yarn link
cd to swapr-dApp and run yarn link @swapr/sdk
All types/missing imports should work fine now.

After you're done playing with linked repo you need to unlink local build. To do this, in your swapr-dApp run yarn unlink @swapr/sdk && yarn install --force

[denciu]

LGTM