[BD-9345][BpkPrice] Add a new icon property to BpkPrice

[wuyq0808]

Changes

1. Adds a new icon property to BpkPrice.
2. Includes small improvements to the HTML structure and CSS properties.

Design

Figma link

Screenshots

Large	Small	Right aligned

Remember to include the following changes:

• Ensure the PR title includes the name of the component you are changing so it's clear in the release notes for consumers of the changes in the version e.g [KOA-123][BpkButton] Updating the colour
• README.md (If you have created a new component)
• Component README.md
• Tests
• Accessibility tests
  • The following checks were performed:
    • Ability to navigate using a keyboard only
    • Zoom functionality (Deque University explanation):
      • The page SHOULD be functional AND readable when only the text is magnified to 200% of its initial size
      • Pages must reflow as zoom increases up to 400% so that content continues to be presented in only one column i.e. Content MUST NOT require scrolling in two directions (both vertically and horizontally)
    • Ability to navigate using a screen reader only
• Storybook examples created/updated
• For breaking changes or deprecating components/properties, migration guides added to the description of the PR. If the guide has large changes, consider creating a new Markdown page inside the component's docs folder and link it here

[skyscanner-backpack-bot]

Visit https://backpack.github.io/storybook-prs/3742 to see this build running in a browser.

[skyscanner-backpack-bot]

Browser support

If this is a visual change, make sure you've tested it in multiple browsers.

Generated by 🚫 dangerJS against 43aa593

[wuyq0808]

Reorganize the elements for better clarity: When aligned right, the trailing text appears on a new line and is wrapped in a <div>. Otherwise, it remains inline and is wrapped in a <span>.

[anambl]

why does it need to be moved outside the span if it's aligned right?

[wuyq0808]

If aligned right, the trailing text appears on a new row, so it should be placed in a separate div within the flex container instead of a span, which is more suited for inline text.

[wuyq0808]

What we had if aligned right:

<div>{leadingText}</div>
<div>
  <span>{price}</span>
  <span>{trailingText}</span>   // 2 spans displayed in 2 rows
</div>

After change:

<div>{leadingText}</div>
<div>
  <span>{price}</span>
  <span>{icon}</span>  // 2 spans displayed in the same row
</div>
<div>
  <span>{trailingText}</span>
</div>

Does this make it clearer?

[wuyq0808]

Replace text-align with align-items to simplify the code.

[wuyq0808]

Rename the css class name to better reflect the main part of the component.

[wuyq0808]

Use margin-inline-end for simplification.

[wuyq0808]

If ? is placed before the type Node, the IDE shows a warning about a missing required property in the example code.
I looked it up and found that placing ? after the property name is the correct syntax in Flow. Is there any context on why we place the ? before the type?

[anambl]

I think it might be that when we first started using flow ? was only supported before the type because looking at other flow'ed components, they all follow the same syntax. You're right though that the docs show it should be place after the property name.