Weather App: Add note about dynamic import()

[MaoShizhong]

Because

Before #28347, the old weather API included icon URLs in the JSON response, so no asset imports would be needed. With VisualCrossing, they don't include any, so you'd have to gather assets (which they provide separately) and import them.

It's a common question in the community about not having to statically import loads of assets individually for dynamic JS. The help typically involves advising about exploring dynamic import(). At this point, learners should be able to make sense of handling async dynamic imports for this project, it just was never previously mentioned so many people have no idea it even exists.

I think it's sensible to mention it and let learners decide what to do with it.

This PR

• Adds note about dynamic import() function for dynamically loading bundled assets

Issue

N/A

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