docs: Add CONTRIBUTING.md (#531)

CONTRIBUTING.md

@@ -0,0 +1,92 @@
+## Welcome
+You have made your way to the contributing guidelines for DefraDB! You are about to be part of a wave making databases decentralized and more powerful.
+
+This document is to help you with the process of contributing to the project. First recommendation is to become familiar with the [project documentation](https://docs.source.network/). Familiarity with [Git](https://training.github.com/), [Go](https://go.dev/doc/install), and [Github](https://docs.github.com/) is assumed.
+
+All contributions are appreciated, whether it's identifying problems, highlighting missing features, or contributing to the codebase in straightforward or complex ways.
+
+You're invited to join the [Source Network Discord](discord.source.network), where you can discuss ideas, ask questions, and find inspiration for what to build next.
+
+
+## Getting started
+Obtain the repository, then build and run it.
+```shell
+git clone https://github.com/sourcenetwork/defradb.git
+cd defradb
+make start
+```
+
+Refer to the [`README.md`](./README.md) and project documentation for usage examples.
+
+
+## Development flow
+
+Methodologies the project follows:
+
+- **Issue-driven development**: Every pull request links to issue(s).
+- **[Squash and merge](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/incorporating-changes-from-a-pull-request/about-pull-request-merges)**: Commits of a pull request are squashed into one before being merged onto the `develop` branch.
+- **[Conventional commits](https://www.conventionalcommits.org/en/v1.0.0/)**: Every commit message is of the `<type>: <description>` format in which "type" is one of `feat`, `fix`, `tools`, `docs`, `perf`, `refactor`, `test`, `ci`, `chore`.
+
+Basic development flow:
+1. Make changes.
+2. Usually, write tests of the changed behavior.
+3. Ensure that `make test` and `make lint` are passing.
+
+Creating an issue:
+1. On [github.com/sourcenetwork/defradb/issues](https://github.com/sourcenetwork/defradb/issues), click "New issue".
+2. Select the relevant issue type.
+3. Fill the issue template.
+
+Submitting a contribution:
+
+1. Fork the repository and with your changes create a branch following the convention `<your-name>/<type>/<description>`, for example `octavio/feat/compression-lru-data`.
+2. Create a pull request targeting the `develop` branch. Link the relevant existing issue(s), and create one if no related issue exists yet. Follow the instructions of the pull request template. Use a verb in the PR title to describe the code changes.
+3. Read through and accept the Contributor License Agreement, if it's your first contribution.
+4. Request review from the *database-team*. Discuss and adapt the pull request accordingly.
+5. If approved, click "Squash and merge" to squash it into one commit and to merge in `develop`. Make sure the title of the commit follows the *Conventional Commits* convention.
+
+
+## Testing
+
+`make test` to run the unit tests and integration tests.
+
+`make lint` to run the linters.
+
+`make bench` to run the benchmark suite. To assess the difference between a branch's results and the `develop` branch's results, execute the suite on both outputting the results to files, and compare the two with e.g. `benchstat develop.txt current.txt`. To install `benchstat` use `make deps:bench`.
+
+`make test:changes` to run a test suite detecting breaking changes. Breaking changes need to be accompanied by documentation in `docs/data_format_changes/` for the test to pass.
+
+
+## Documentation
+The overall project's documentation is found at [docs.source.network](https://docs.source.network), and its source at [github.com/sourcenetwork/docs.source.network](https://github.com/sourcenetwork/docs.source.network).
+
+The code documentation, doc comments, can be viewed as a website:
+```shell
+go install golang.org/x/pkgsite/cmd/pkgsite@latest
+cd your-path-to/defradb/
+pkgsite
+# open http://localhost:8080/github.com/sourcenetwork/defradb
+```
+- [go.dev/doc/comment](https://go.dev/doc/comment) has guidelines on writing Go doc comments.
+
+`docs/cmd/` is where auto-generated documentation of the `defradb` command-line program is.
+
+`docs/data_format_changes/` details the historical breaking changes to data persistence.
+
+
+## Additional information
+
+This section includes good-to-know information for advanced contributors.
+
+Dependency management:
+- `go mod tidy` should be performed by pull requests changing dependency requirements.
+- The project uses `dependabot` for automatic creation of pull requests updating dependencies.
+
+Peer review of pull requests:
+- Using the [Conventional Comments](https://conventionalcomments.org/) methodology is recommended.
+
+Licensing:
+- The [BSL license header](./licenses/BSL.txt) must be included at the top of every code file.
+
+Project management:
+- [Milestones](https://github.com/sourcenetwork/defradb/milestones)  and a [project board](https://github.com/orgs/sourcenetwork/projects/3) are used to coordinate work on releases.