feat: add nani-account

[nerderlyne]

Pull Request Checklist

• Did you add new tests and confirm existing tests pass? (yarn test)
• Did you update relevant docs? (docs are found in the site folder, and guidelines for updating/adding docs can be found in the contribution guide)
• Do your commits follow the Conventional Commits standard?
• Does your PR title also follow the Conventional Commits standard?
• If you have a breaking change, is it correctly reflected in your commit message? (e.g. feat!: breaking change)
• Did you run lint (yarn lint:check) and fix any issues? (yarn lint:write)
• Did you follow the contribution guidelines?

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PR-Codex overview

Detailed summary

• Added NaniAccountProviderConfig type in packages/accounts/src/nani-account/types.ts.
• Exported NaniAccount and createNaniAccountProvider in packages/accounts/src/index.ts.
• Created createNaniAccountProvider function in packages/accounts/src/nani-account/provider.ts.
• Added getDefaultNaniAccountFactoryAddress utility function in packages/accounts/src/nani-account/utils.ts.
• Defined NaniAccountFactoryConfigSchema and NaniAccountProviderConfigSchema in packages/accounts/src/nani-account/schema.ts.
• Added NaniAccountFactoryAbi in packages/accounts/src/nani-account/abis/NaniAccountFactoryAbi.ts.
• Added nani-account.ts snippet in site/snippets/nani-account.ts.
• Added tests for NaniAccount in packages/accounts/src/nani-account/__tests__/account.test.ts.
• Updated documentation in site/smart-accounts/accounts/nani-account.md.

The following files were skipped due to too many changes: site/smart-accounts/accounts/nani-account.md, packages/accounts/src/nani-account/account.ts, packages/accounts/src/nani-account/abis/NaniAccountAbi.ts

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[moldy530]

couple nits, but LGTM