Feat/lp zapping

[karczuRF]

Summary

Fixes #491

Beta version of LP-Zapping feature!

LP-Zapping allows to swap any erc-20 token (but native currency is also supported!) for 2 different tokens and add liquidity to the pool with just 1-click!
It works also in another direction, so allows to remove liquidity from the pool and swap pool's tokens to any different token, ofc also with 1-click.

Important node
Since this is quite complex feature there still can be bugs which I couldn't find, so keep in mind this is still Beta version!
Designs still needs to be created (eg zap details, slippage etc) and will be added as soon as we have them.
The latest version of zap contract can be found here: https://github.com/ImpeccableHQ/swapr-lp-zapping/blob/main/contracts/Zap.sol

Test Zap contract was deployed on Gnosis only, so for any other network zap is not yet available!
Contract details can be found here: https://blockscout.com/xdai/mainnet/address/0x618471C54443586E97FD81cDc357DCB9a1db8f87

To Test

1. Open Swapr
2. Go to Zap page. This can be done with different ways:

• simply go to Zap tab
• use Liquidity tab and '+ZAP'
• use Liquidity tab, select any Pair and if this pair is supported for Zap, the button Zap will be active

4. Select token / pair for zapping
5. Check approval flow
6. Check if transactions passed/failed
7. Check button/popup texts and colors
8. Check account's details if zap tx is listed
9. Play around and have fun!