feat: add showPopup method on controller for web platform

[Pierre-Monier]

Fix issue #1192

I add a method on the MapboxMapController to display a popup when features of a given layer are hovered.

The method is named showPopupOnFeatureHover and it only does stuff if we are on the web, i.e _mapboxGlPlatform is MapboxWebGlPlatform.

And all it does it to create a Popup object and pass it to a method on the MapboxWebGlPlatform to actually display/hide the popup when a feature is hovered/ stop being hovered.

This implementation doesn't change the MapboxGlPlatform interface, because it's only web related, so it shouldn't be in the interface.

The displayed text is retrieved from the geoJson data, at the key description , like this example

[Thematt69]

Hello @felix-ht, I saw you discussed this modification, is it possible to review? I have the same need as @Pierre-Monier

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Thematt69]

Hello @tobrun, is it possible for you to look at this pull request?
I'm currently developing a Flutter app (mobile and web) and we're using quite a bit of functionality from this package.
I'll leave you the link to the site if you want to watch, https://qualite-riviere.lesagencesdeleau.fr/

Thanking you in advance.