Add optional alt prop to POS image

[BrittaEvansFenton]

Background

Adds alt text as an optional prop
Follows what is expected: https://github.com/Shopify/ui-api-design/tree/main/components/Image

Questions

have I missed anything?

Solution

(Describe your solution, why this approach was chosen, and what the alternatives/impacts may be)

🎩

• ...

Checklist

• I have 🎩'd these changes
• I have updated relevant documentation

[github-actions]

We detected some changes in packages/*/package.json or packages/*/src, and there are no updates in the .changeset directory. If the changes are user-facing and should cause a version bump, run yarn changeset to track your changes and include them in the next release CHANGELOG. If you are making simple updates to repo configuration, examples, or documentation, you do not need to add a changeset.

[NathanJolly]

Suggested change

	src?: string;
	alt?: string;
	/**
	* The url of the image.
	**/
	src?: string;
	/**
	* Alternative text for the image.
	**/
	alt?: string;

[NathanJolly]

I think these just need comments!

[js-goupil]

@BrittaEvansFenton should we merge this? Or make the changes suggested?