Currently we do not support providing the image URL for custom tokens via wallet_watchAsset because we don't support getting a remote resource yet.

Test Plan:

1. Visit https://www.coingecko.com/en/coins/railgun and click on the fox icon to add suggest token

2. Prompt should show up for adding suggest token (will be asking to unlock first if wallet is locked), make sure the icon is displayed as expected here.
   

3. Click to add the token and check the token is added to user visible asset list and make sure the icon is displayed as expected here.