Buildkite integration for Rust project

[oguzkocer]

Tasks

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1. Build the project for all relevant architectures
2. Run unit tests
3. Generate docs (Don't publish until the project is open source: Publish Rust documentation to docs.rs #16)
4. Run clippy
5. Run rustfmt

[jkmassel]

Run unit tests
Run clippy

These are addressed by #35

Run rustfmt

This is addressed by #47

[jkmassel]

Generate docs

#55 should handle this

[jkmassel]

Build the project for all relevant architectures

I think we have this for Rust-specific needs. #13 and #14 address the specific architectures needed for Kotlin / Swift, so I'd be ok to check that item off and close this issue.