Bump tokio from 0.2.13 to 0.2.22 (#18)

Bumps [tokio](https://github.com/tokio-rs/tokio) from 0.2.13 to 0.2.22.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-0.2.13...tokio-0.2.22)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Evan Pete Walsh <epwalsh10@gmail.com>

Author: dependabot[bot]