Initial ERC-8004 support

[tjanez]

Start adding initial support for ERC-8004: Trustless Agents to the ROFL App.

Ideas:

• Opt-in check box to enable adding ROFL-8004 startup image to the ROFL-powered application a user is creating (see: rofl-8004: Initial commit and example, cleanups erc-8004#5).
  Could be part of all the current templates' flow or the Custom App flow.
• Show ERC-8004 registration/validation for ERC-8004-enabled apps in the frontend.