[dartpad_ui] Add splash screen

[cheymos]

Added a simple splash screen so that when you open dartpad.dev you don't have to look at a white screen. 🙂
Implemented with mobile devices and theme change in mind.

Mobile Demo

Screen.Recording.2024-11-09.at.21.27.45.mov

Desktop Demo

Screen.Recording.2024-11-09.at.21.25.07.mov

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[cheymos]

@parlough Hi! What do you think about this PR?

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[cheymos]

@devoncarew Hi! I'm sorry if I'm tagging you. But could you please tell me how I should deal with this PR?

[devoncarew]

Thanks for the contribution! I like that you've moved the index.html styles into a new file - I think that helps with readability.

Wrt the white flash at startup, I do see it now myself; I expect that it's noticeable when using the dark theme. We probably don't need the dart icon as part of the splash screen, and, we may want to make the exit animation for the splash screen shorter as it would otherwise delay visibility by a 1/2 sec.

You may generally want to start with an issue instead of a PR for feature contributions - it would help save you time if we decide against the feature in general. But I'm probably not the right reviewer; I'll bump you over to @johnpryan and @parlough.

[devoncarew]

I assume this color is the color we'd settle into after we've started up in the light theme?

[cheymos]

Yeah, that's right.

[devoncarew]

Same with this with the dark theme?

[cheymos]

Yep.

[cheymos]

Thanks for the contribution! I like that you've moved the index.html styles into a new file - I think that helps with readability.

Wrt the white flash at startup, I do see it now myself; I expect that it's noticeable when using the dark theme. We probably don't need the dart icon as part of the splash screen, and, we may want to make the exit animation for the splash screen shorter as it would otherwise delay visibility by a 1/2 sec.

You may generally want to start with an issue instead of a PR for feature contributions - it would help save you time if we decide against the feature in general. But I'm probably not the right reviewer; I'll bump you over to @johnpryan and @parlough.

You're right, I was a bit rushed with the PR though. I'll start with issues next time.
These changes didn't take me long to make, so I could redo them if needed.