[MBL-1457] Create empty state view for PPO

[ifosli]

📲 What

Add an empty state view to the pledged projects overview.

Note: I didn't add a view model for the empty state view since it's so simple that I don't feel like it would add value. If anyone disagrees, however, let me know!

Note: This only kind of supports dynamic type: if the trait collection changes after the view has rendered, it doesn't re-render. The rest of our app is already pretty inconsistent about behavior when the trait collection changes, so I don't think this is worse than the current app experience. We may want to revisit this if/when we re-do the design system, though.

👀 See

Jira, figma

Screen recording	Large text

♿️ Accessibility

• Tap targets use minimum of 44x44 pts dimensions
• Works with VoiceOver
• Supports Dynamic Type

✅ Acceptance criteria

• Empty state view looks good
• Empty state button works

(we're not testing that the empty state view shows up when it should yet)

⏰ TODO

• Test voiceover
• Pull button styling out into a helper as part of https://kickstarter.atlassian.net/browse/MBL-1452 (not planned for this pr)

[scottkicks]

I agree that a View Model for this view doesn't add enough value to warrant one. There also aren't any @State objects to manage either.

LGTM 👍 Yay SwiftUI!