feat: speedy css tip animated loader post

[jh3y]

Changes proposed in this pull request:

• Quick post for "Speedy CSS Tip" ⚡

When you're ready to submit your PR, don't forget to add the $-presubmit label.

[chrome-devrel-review-bot]

Hello! This is an automated review by our custom reviewbot. It updates automatically when code or GitHub comments in this pull request are created or updated.

Requested changes

If there are any common problems with the content files you created or modified, they will be listed here.

src/site/content/en/blog/speedy-css-tip-animated-loader/index.md

• Please add a single newline character to the end of the file. Some programs have trouble with files that don't end with a newline. Affected lines: 106

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