Add new icons

[HiDeoo]

Description

As discussed on Discord, this PR adds new icons to the Starlight icon set:

• left-carret so we have all caret directions
• up-arrow and down-arrow so we have all arrow directions
• download and cloud-download

Ran all SVGs through SVGOMG to optimize them.

[changeset-bot]

🦋 Changeset detected

Latest commit: 9000a2a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@astrojs/starlight	Patch

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[netlify]

✅ Deploy Preview for astro-starlight ready!

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🔨 Latest commit	97c9cb7
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Lighthouse	1 paths audited Performance: 100 (no change from production) Accessibility: 100 (no change from production) Best Practices: 100 (no change from production) SEO: 100 (no change from production) PWA: - View the detailed breakdown and full score reports

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[delucis]

Looks perfect! I checked the deploy preview and the icons display correctly, the names and ordering makes sense, and the SVGOMG compression also looks like it matches our existing similar icons.

Thanks @HiDeoo!