Update store plugin's docs to match the new rework

[Legend-Master]

Description

• What does this PR change? Give us a brief description. Update store plugin's docs to match the new rework refactor(store)!: more reworks plugins-workspace#1860
• Closes Plugin Store StoreExt ctx doesnt exist plugins-workspace#1890
• Closes [bug] cannot find function with_store in crate tauri_plugin_store plugins-workspace#1908

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[Legend-Master]

I'll merge this for now, we can improve this later on, don't want to leave the docs outdated for too long