Clarify the usage of the symbol "@" in the keys on the guide async-storage/website/docs/Usage.md

[KirillBorunov]

What happened?

In the examples you are using the symbol "@" in the key argument, but there is no explain why, and if this is required.

https://github.com/react-native-async-storage/async-storage/blob/ba983157c127f77b5bb0ece3c09e3077c978bc6d/website/docs/Usage.md?plain=1#L26

https://github.com/react-native-async-storage/async-storage/blob/ba983157c127f77b5bb0ece3c09e3077c978bc6d/website/docs/Usage.md?plain=1#L38

https://github.com/react-native-async-storage/async-storage/blob/ba983157c127f77b5bb0ece3c09e3077c978bc6d/website/docs/Usage.md?plain=1#L54

https://github.com/react-native-async-storage/async-storage/blob/ba983157c127f77b5bb0ece3c09e3077c978bc6d/website/docs/Usage.md?plain=1#L70

Version

https://react-native-async-storage.github.io/async-storage/docs/usage

What platforms are you seeing this issue on?

• [X] Android
• [X] iOS
• [X] macOS
• [X] Windows
• [X] web

System Information

Issue is about the docs.

Steps to Reproduce

Not needed.

[krizzu]

It's nothing special about it, it's fine to ignore