[Wallets > v5] Proof read, improve

[pyAndr3w]

• Proof-read and improve /standard/wallets/v5

including:

• Add a description action list validation for Wallet v5
• Add a description of the Wallet v5 wallet_id scheme and align it with the implementation used in the official wrapper (see Unspecified wallet_id derivation scheme tonkeeper/w5#247 | Unspecified wallet_id derivation scheme ton-blockchain/wallet-contract-v5#290).
• Update /standard/wallets/how-it-works#subwallet-id to add a separate note about the special wallet_id scheme used by Wallet v5.