[NT-328] Add min pledge label to pledge screen

[dusi]

📲 What

Adds min pledge amount label with description of what the minimum amount is.

🤔 Why

This is a product requirement.

🛠 How

Simply adds label and shows/hides it based on whether it is a reward or no reward (hidden for no rewards).

👀 See

Before 🐛	After (no reward) 🦋	After (reward) 🦋

♿️ Accessibility

• Works with VoiceOver
• Supports Dynamic Type

✅ Acceptance criteria

• Min pledge label should SHOW and show the correct amount & currency for reward (on the
  pledge screen)
• Min pledge label should NOT SHOW for no reward (on the pledge screen)

⏰ TODO

• Use generated string when it's available

[Scollaco]

Nice @dusi ! I just left a couple of minor comments 🥇

[Scollaco]

The string (untranslated) seems to be available. So I think we can replace this line with

Strings.The_minimum_pledge_is(min_pledge: Format.currency(min, country: project.country, omitCurrencyCode: false))

[Scollaco]

I know that this was already merged, but I wonder if creating a variable to better describe what exactly the UIView(frame: .zero) is would be more readable.
Something like:

let spacer (or whatever name) = UIView(frame: .zero)

_ = ([
      self.titleLabel,
      self.adaptableStackView,
      self.minPledgeAmountLabel,
      spacer
    ], self.rootStackView)

[dusi]

I'll add a prop

[Scollaco]