Add SENTENCIFY

[hellochanyoung]

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Summary by cubic

Added SENTENCIFY to the S resources list as a paraphrasing tool to expand writing resources.
Includes name, description, categories, URL, and keywords.

^{Written for commit 8638335. Summary will update on new commits.}

[github-actions]

New resource link: https://www.sentencify.ai/en/

[cubic-dev-ai]

No issues found across 1 file