toast: add promise based usage

[jsorb84]

Added a section with an example for promise based toasts.

Closes #

📝 Description

just added a how to for promise toasks

⛳️ Current behavior (updates)

N/A

🚀 New behavior

N/A

💣 Is this a breaking change (Yes/No):

📝 Additional Information

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Name	Status	Preview	Updated (UTC)
chakra-ui-docs	✅ Ready (Inspect)	Visit Preview	Sep 11, 2023 10:55pm