I added one sentence to the ## Develop section of README.md: "This project uses the Rust 2021 edition." The edition comes from edition = "2021" in Cargo.toml. cargo test passes, though the project has no tests, so that run only confirms it builds.
The issue title says "minimum Rust version", but Cargo.toml has no rust-version field. The sentence therefore names only the edition, as the issue body asks, and doesn't state a minimum compiler version.