Book: Starkli 101 uses deprecated code in the tutorial

[arad-starkware]

The src/lib.cairo specified in the tutorial no longer works on the current starknet version (2.9.2 as of writing this issue), and the version specified in the page is no longer available for downgrade.
Adding

    use starknet::storage::{
        StoragePointerReadAccess, StoragePointerWriteAccess,
    };

inside the my_contract module, and changing the decoration #[external(v0)] to #[abi(embed_v0)] fixes the issue for the current starknet version.