fix: add loading=async to the urls with callbacks

[nora-soderlund]

This PR adds loading=async as a combination with the callback parameter to resolve the warning message.

From the Discord:

hello, do you guys know how to get rid off the warning below while using APIProvider component from '@vis.gl/react-google-maps' ? I don't see there any flag to set regarding loading type, obviously I could load the maps in old vanilla JS way but it's not a point while I have installed the library package 😦

"Google Maps JavaScript API has been loaded directly without loading=async. This can result in suboptimal performance. For best-practice loading patterns please see https://goo.gle/js-api-loading"

From the documentation:

loading: The code loading strategy that the Maps JavaScript API can use. Set to async to indicate that the Maps JavaScript API has not been loaded synchronously and that no JavaScript code is triggered by the script's load event. It is highly recommended to set this to async whenever possible, for improved performance. (Use the callback parameter instead to perform actions when the Maps JavaScript API is available.) Available starting with version 3.55.

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Fixes #<issue_number_goes_here> 🦕

[usefulthink]

Looks good to me, but eslint didn't like something about the formatting. Can you run npm run format and push again?

[nora-soderlund]

Yeah, sorry, did this over the web. I've fixed the linting @usefulthink :)

[nora-soderlund]

I just noticed that this is the wrong library 😄 I mistakenly thought that the @vis.gl/react-google-maps package uses this repository but it has its own loader.

I guess this is still a valid fix? 😝

[wangela]

Thanks for this fix, @nora-soderlund! Yup, even though this isn't a fix for vis.gl/react-google-maps this is a good fix to incorporate into the js-api-loader.