docs: add vasanth9 as a contributor for code (#813)

Adds @vasanth9 as a contributor for code.

This was requested by JoshuaKGoldberg [in this
comment](#812 (comment))

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Co-authored-by: allcontributors[bot] <46447321+allcontributors[bot]@users.noreply.github.com>

Author: allcontributors[bot]