new icon: celery (original, original-wordmark, plain, plain-wordmark)

[star-lord1234]

Double check these details before you open a PR

• [ ] PR does not match another non-stale PR currently opened
• [ ] PR name matches the format new icon: Icon name (versions separated by comma). More details here
• [ ] PR's base is the develop branch.
• [ ] Your icons are inside a folder as seen here
• [ ] SVG matches the standards laid out here
• [ ] A new object is added in the devicon.json file at the correct alphabetic position as seen here

This PR closes NONE

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Description

This PR adds a new icon for Celery, including:

• icons/celery/celery-original.svg
• icons/celery/celery-wordmark.svg

The SVGs are optimized, validated against the W3C checker, and under 1KB in size.

Checklist

• [x] Icon files are in the correct folder (icons/celery/)
• [ ] SVGs are under 1KB
• [x] SVGs pass W3C validation
• [x] Readme updated automatically by CI