Support safe apps

[oed]

What it solves

Adds support for safe apps. By default no apps are listed, which means that all apps need to be added manually. This is because right now none of the apps are available over IPFS.

Resolves #6

How this PR fixes it

Adds back upstream safe apps. Users can now add the transaction builder as a custom app.

How to test it

Screenshots

Checklist

• I've tested the branch on mobile 📱
• I've documented how it affects the analytics (if at all) 📊
• I've written a unit/e2e test for it (if applicable) 🧑‍💻

[vercel]

@oed is attempting to deploy a commit to the Eternal Safe Team on Vercel.

A member of the Team first needs to authorize it.

[ape-dev-cs]

I've taken this for a spin and it seems to work nicely with the TX builder. More complex safe apps however tend to fail (tested a few from https://github.com/safe-global/safe-apps-list/blob/main/config/appsList.js). Any clues as to why this is? They mostly just don't detect that they're being run through the safe UI, or fail to load all together (due to x-frame-options / sameorigin policy.