Ensure code format

[trusktr]

Summary

We're using prettier, so ensure we check code format as part of the lint script. Also add a prettier script for manually formatting the whole code base.

Related issue, if any:

• https://github.com/docsifyjs/docsify/issues/2104

What kind of change does this PR introduce?

Build-related changes Repo settings

For any code change,

• [x] Related documentation has been updated, if needed
• [x] Related tests have been added or updated, if needed

Does this PR introduce a breaking change? (pick one)

No

Tested in the following browsers:

• [x] Chrome
• [x] Firefox
• [x] Safari
• [x] Edge

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Name	Status	Preview	Updated (UTC)
docsify-preview	✅ Ready (Inspect)	Visit Preview	Jul 17, 2023 5:50am

[trusktr]

Oops! I hit turned on auto-merge, and it merged this into the other PR. Closing, trying again.