flutter create should make an app with a non-white splash screen

[collinjackson]

(based on @xster's proposal in #8127)

When running flutter create, the default launch storyboard is white. Devs will likely want to show a custom screen while the app is loading. Consider putting a placeholder splash screen in the template app, so devs can just drop in new assets and be done with it.

Here are some resources that discuss configuring splash screens.

iOS: https://docs.nativescript.org/publishing/creating-launch-screens-ios

Android: https://www.bignerdranch.com/blog/splash-screens-the-right-way/

[xster]

I would amend that if possible, it would be great to not encourage users to dive into the /android and /ios folders manually at all and just generate this automatically from some .yaml in flutter space.

[abarth]

Developers are going to need to dive into the android and ios folders to complete their apps. For example, they'll need to do that to configure launcher icons. I think it's reasonable for the default project template to have an example splash screen (much like we provide an example launcher icon), but I don't think we add much value by intermediating the splash screen.

[Hixie]

How does this differ from #8127 ?

[collinjackson]

This bug is about having a default iOS splash screen that isn't white (e.g. Flutter logo)

#8127 is about removing the black flicker between the splash screen and the main app being rendered.

[eseidelGoogle]

@xster mentioned interest in this.

[eseidelGoogle]

Speculatively moving to M3.

[eseidelGoogle]

The reason to consider this for M2 is to make the presentations better during Flutter talks at I/O.

[eseidelGoogle]

@xster you were working in this area recently, curious if this status has changed?

[xster]

I didn't have plans but it's fairly easy. I can put something together.