Support custom transactions in Eternal Safe

[oed]

Currently eternalsafe.eth.link only support sending erc20 and erc721 tokens. We need to enable the custom transaction builder in order to send transactions to the config actor.

[oed]

Bu adding support for Safe apps, users can manually add the https://apps-portal.safe.global/tx-builder/ tx builder app in the Safe app interface to make custom transactions.

[oed]

I have a partial implementation here: eternalsafe/wallet#58

[brunocalza]

The same applies here