Add navigation bar to the avatar picker

[pinarol]

Closes #343

Description

Adds navigation bar. I used NavigationView for now since it is supported in iOS 15. NavigationStack is supported only for iOS 16+.

• Adds "Done" button to close the picker
• Gravatar icon opens Safari with profile url

Updates the "Discover Your Gravatar Card" to "View profile" based on designs. Ties the action to open the profile in Safari.

Refactors some of the paddings based on the designs.

Testing Steps

• Play around with the SwiftUI demo app.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Gravatar UIKit Prototype Build by scanning the QR code below to install the corresponding build.

	App Name	Gravatar UIKit Prototype Build
	Build Number	1118
	Version	1.0
	Bundle ID	com.automattic.gravatar-sdk-demo-uikit.prototype-build
	Commit	4a4dd0b
	App Center Build	Gravatar SDK Demo - UIKit #54

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Gravatar SwiftUI Prototype Build by scanning the QR code below to install the corresponding build.

	App Name	Gravatar SwiftUI Prototype Build
	Build Number	1118
	Version	1.0
	Bundle ID	com.automattic.gravatar-sdk-demo-swiftui.prototype-build
	Commit	4a4dd0b
	App Center Build	Gravatar SDK Demo - SwiftUI #53

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[etoledom]

Looks good to me!

There's one detail which troubles me a bit, but I don't think there's much we can do without making things overly complicated:

SFSafariViewController has a custom modal presentation animation which emulates a navigation push. It's the standard animation in which the in-app browser is presented.

CleanShot.2024-08-22.at.16.43.06.mp4

SwiftUI doesn't seem to be compatible with these custom presentation animations, and we lose the standard SFSafariViewController presentation.

I saw that most resources online mentions using .sheet presentation, which is the easiest. I tested using NavigationLink but it won't work either.
The closest is to use .fullScreenCover() instead of .sheet(), so it presents full screen.

The complex option I saw is to present SFSafariView in UIKit side from UIApplicationDelegate or UIWindow, and call it from SwiftUI using a global reference. But we also don't have the UIKit context in a pure swiftUI app. ¯_(ツ)_/¯

Either way, lets go along with this one. Hopefully Apple will do something about this at some point.

Either way, I'm fine how it is now

[pinarol]

I liked "fullScreenCover" better. 👍 For now it seems like the best we can get out of SwiftUI about this.