chore: contributing.md (#91)

Author: prestwich

CONTRIBUTING.md

@@ -0,0 +1,41 @@
+# Contributing to Trevm
+
+:balloon: Thanks for your help improving the project! We are so happy to have
+you!
+
+## Conduct
+
+This repo adheres to the [Rust Code of Conduct][coc]. This describes
+the _minimum_ behavior expected from all contributors. Failure to maintain civil
+behavior will result in a ban.
+
+[coc]: https://www.rust-lang.org/policies/code-of-conduct
+
+## Pull Requests
+
+Before making a large change, it is usually a good idea to first open an issue
+describing the change to solicit feedback and guidance. This will increase the
+likelihood of the PR getting merged.
+
+When opening a PR **please select the "Allow Edits From Maintainers" option**.
+We maintain code quality and style standards, and require commit signing. This
+option allows us to make small changes to your PR to bring it in line with
+these standards. It helps us get your PR in faster, and with less work from you.
+
+## Development Basics
+
+Before submitting a PR we recommend you run the following commands to ensure
+your code is properly formatted and passes all tests:
+
+```sh
+cargo +nightly fmt --all
+cargo clippy --all-features
+cargo test --all-features
+cargo test --no-default-features
+```
+
+### Contributions Related to Spelling, Grammar, and other trivial changes
+
+At this time, we will not be accepting contributions that only fix spelling or
+grammatical errors in documentation, code or
+elsewhere.