feat: add small size for `Quantity` component

[lauthieb]

Changes description

Closes #1360

Checklist

• [x] Make sure you are requesting to pull a topic/feature/bugfix branch. Please, don't request directly from your main!
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• [x] Check your code additions will fail neither code linting checks.
• [x] I have reviewed the submitted code.
• [x] I have tested on related showcases.
• [x] If it includes design changes, please ask for a review design-system-core-team-design GitHub team.

Does this introduce a breaking change?

• No