add contributing doc (risc0#1215)

Opening draft for visibility, would like to get risc0#1214 completed before
this comes in to avoid having to include the version pinning semantics
into this doc.

CONTRIBUTING.md

@@ -0,0 +1,75 @@
+# Contributing to risc0
+
+Thank you for your interest in contributing to RISC Zero! We welcome contributions from everyone.
+
+If you have any questions about contributing, or about the project in general, please ask in our [Discord channel](https://discord.gg/risczero).
+
+## Quick Start
+
+To run the test suite, the following dependencies are needed:
+
+#### [Git Large File Storage](https://docs.github.com/en/repositories/working-with-files/managing-large-files/installing-git-large-file-storage)
+
+Once installed, run:
+
+```console
+git lfs install
+git lfs pull
+```
+
+#### [Rust](https://www.rust-lang.org/tools/install)
+
+```console
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+```
+
+#### [RISC Zero toolchain](https://dev.risczero.com/api/zkvm/quickstart#1-install-the-risc-zero-toolchain)
+
+The RISC Zero toolchain must match the version of crates you are compiling.
+
+When testing and running examples within this library, you can install `cargo-risczero` from source:
+
+```console
+cargo install --force --path risc0/cargo-risczero
+cargo risczero install
+```
+
+Otherwise, if using a stable version branch, you can install `cargo-risczero` through the standard flow:
+
+```console
+cargo install cargo-binstall
+cargo binstall cargo-risczero
+cargo risczero install
+```
+
+Optionally, you can specify which version of `cargo-risczero` to install with:
+
+```console
+cargo binstall cargo-risczero@<version>
+```
+
+> NOTE: It is only important that you install `cargo-risczero` with a matching version of the `zkvm` crate when interacting with the proof system as a separate, pre-built process ([`ExternalProver`](https://docs.rs/risc0-zkvm/latest/risc0_zkvm/struct.ExternalProver.html)), which is currently the default. If you are using the `prove` feature on the `risc0-zkvm` crate for the host, this will compile the proving system into the host binary.
+
+#### [Foundry](https://book.getfoundry.sh/getting-started/installation)
+
+```console
+curl -L https://foundry.paradigm.xyz | bash
+foundryup
+```
+
+#### xtask wasm tools (if testing [browser-verify](./examples/browser-verify))
+
+```console
+cargo xtask install
+cargo xtask gen-receipt
+```
+
+## PR Checklist
+
+Before submitting a PR, ensure the following:
+
+1. Fork the `risc0` repository and create a new branch there to do your work.
+2. Format with `cargo fmt --all`.
+3. Lint with `cargo clippy --all-targets`.
+4. Tests pass with `cargo test -F default -F prove --workspace`
+5. Open a PR against the `main` branch.

website/docs/contributors-guide.md

@@ -6,7 +6,7 @@ _This page describes guidelines for community contributions to this [website](ht
 >
 > - Make suggestions or report bugs via [GitHub issues](https://github.com/risc0/risc0/issues)
 > - Contribute website content or give feedback on [open pull requests](https://github.com/risc0/risc0/pulls)
-> - Contribute to the [main zkVM project](https://github.com/risc0/risc0)
+> - Contribute to the [main zkVM project](https://github.com/risc0/risc0) (see [CONTRIBUTING](https://github.com/risc0/risc0/blob/main/CONTRIBUTING.md))
 > - Contribute to our tutorials and how-to guides for our [templates](https://github.com/risc0/risc0/tree/main/templates) and [Rust examples](https://github.com/risc0/risc0/tree/v0.18.0/examples)
 > - Ask questions on [Discord](https://discord.gg/risczero)