docs: add pkeugine as a contributor

[allcontributors[bot]]

Adds @pkeugine as a contributor for review.

This was requested by pkeugine in this comment

[pkeugine]

@all-contributors please @pkeugine for mentor

[allcontributors[bot]]

@pkeugine

I could not determine your intention.

Basic usage: @all-contributors please add @someone for code, doc and infra

For other usages see the documentation

[pkeugine]

@all-contributors please add @pkeugine for mentor

[allcontributors[bot]]

@pkeugine

I couldn't determine any contributions to add, did you specify any contributions? Please make sure to use valid contribution names.