[FEATURE] ERC-20, 721 support

## Is your feature request related to a problem? Please describe.

I think it would be nice to add support for ERC-20 and ERC-721 as widely used token standards.

## Describe the solution you'd like
I would like to support the following features for ERC-20 and ERC-721.

- `abi`
- `token_info`
- `user_position`
- `user_notification`
