docs: add Rust deploy guide and runnable example for Datum compute

[scotwells]

What this adds

A complete, runnable path for a developer to take a Rust HTTP service from source to a live, reachable Instance on Datum compute.

• Guide at docs/guides/deploy-a-rust-app.md — the step-by-step walkthrough: write the service, package it as a Unikraft unikernel with kraft, deploy with datumctl compute, and verify the Instance is serving traffic.
• Ready-to-deploy example at examples/hello-rust/ — every file the guide describes, materialized so a developer can clone the folder and go straight from source to a running Instance:
  • src/main.rs — the std-only Rust HTTP service
  • Cargo.toml — release profile tuned for a small static binary
  • Dockerfile — static, position-independent (PIE) musl build with a self-check that fails fast on a wrong-shaped binary
  • Kraftfile — Unikraft Cloud packaging config
  • workload.yaml — the Datum Workload manifest
  • README.md — one-line description, link back to the guide, and the build/deploy commands

Developer experience

Clone examples/hello-rust/, run the kraft cloud ... deploy --no-start build, then datumctl compute deploy -f workload.yaml -y, and curl the resulting Instance. No copy-pasting from the guide required — the example is the guide, made real.

🤖 Generated with Claude Code

[ecv]

it is with a heavy heart i agree we should allow rustaceans to use the platform