feat: create `<PrismicImage>` component

[samlfair]

Types of changes

• [ ] Chore (a non-breaking change which is related to package maintenance)
• [ ] Bug fix (a non-breaking change which fixes an issue)
• [x] New feature (a non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Description

Create a <PrismicImage /> component that renders an img element with src, srcset, width, height, and alt attributes. Accepts class, widths, and imgixParams props.

Checklist:

• [x] My change requires an update to the official documentation.
• [x] All TSDoc comments are up-to-date and new ones have been added where necessary.
• [x] All new and existing tests are passing.

[angeloashmore]

The changes look good! I left two comments re: alt and the srcSet helpers.

Once those changes are in place, I think we'll be good to merge and publish.