docs: add CONTRIBUTING.md

Signed-off-by: Christina Sørensen <christina@cafkafk.com>

CONTRIBUTING.md

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+<!--
+SPDX-FileCopyrightText: 2023-2024 Christina Sørensen
+SPDX-FileContributor: Christina Sørensen
+
+SPDX-License-Identifier: EUPL-1.2
+-->
+
+# Contributing to Nix Weather
+
+Nix Weather is a NixOs adjacent project, and expects contributors to have **at least** a local installation of `Nix` or `Lix` on their development machine.
+
+## DevShell
+
+Currently, `nix-weather` is developed against Lix main branch. We also make use
+of experimental features, including ones still in RFC stage, such as [RFC 0148:
+`pipe-operators`](https://github.com/NixOS/rfcs/pull/148).
+
+The `devShell` in the flake takes care of setting this up for you, so as long as
+you can run that, you shouldn't have to worry.
+
+Further, the devShell includes formatting through `nix fmt`, and testing through
+`nix flake check`, as well as pre-commit-hooks, that ensure any PR is up to
+standard before being submitted. 
+
+We stronly advice working and commiting from inside the devShell. To make this
+easier, use the provided [direnv](https://direnv.net/) configuration by
+installing direnv and running `direnv allow` in the repository root.
+
+## Code Standards
+
+We make use of several standards, including:
+- [Semantic Versioning](https://semver.org/) for version bumps.
+- [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) for commit summaries.
+- [REUSE](https://reuse.software/) for license complicance.
+
+We also make use of code formatters, as well as rust related tooling for
+auditing dependencies have licenses that are compliant with the
+[EUPL-1.2](https://commission.europa.eu/content/european-union-public-licence_en).
+
+Take note that contributions will be legally considered under the EUPL-1.2
+Article 6 "Chain of Authorship" section, essentially a developer certificate of
+origin.
+
+> 6.Chain of Authorship
+>
+> The original Licensor warrants that the copyright in the Original Work granted
+> hereunder is owned by him/her or licensed to him/her and that he/she has the
+> power and authority to grant the Licence.
+>
+> Each Contributor warrants that the copyright in the modifications he/she
+> brings to the Work are owned by him/her or licensed to him/her and that he/she
+> has the power and authority to grant the Licence.
+>
+> Each time You accept the Licence, the original Licensor and subsequent
+> Contributors grant You a licence to their contributions to the Work, under the
+> terms of this Licence.
+
+### Pull-Requests
+
+We currently expect that all commits are functional against `nix flake check`
+and don't introduce any regressions. Further we prohibit merge branch updates,
+and expect all pull requests to have been rebased against the `main` branch
+before being merged.
+
+Long chains of commits should be divided into separate PRs, specially if
+introducing multiple features that  will all need separate review. Ideally, a
+stacked workflow is preferred.
+
+Formatting changes of code created in the PR should be rebased into the commit
+introducing the codebase, **not** be it's own separate commit.
+
+Treewide changes should be added to a `.git-blame-ignore-revs`.
+
+## Code of Conduct
+
+The project is moderated according to the [Contributor Covenant Code of
+Conduct](CODE_OF_CONDUCT.md). We expect all contributions, issues, and other
+project communications made in spaces related to the project to live up to the
+standards set in the code of conduct, and it will be enforced according to the
+`Enforcement Guidelines` it describes.
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported to the community leaders responsible for enforcement at:
+
+matrix: @cafkafk:gitter.im

README.md

@@ -52,3 +52,7 @@ Caching the requisites is a future goal, so that we only have to build the
 down the nix part of the runtime by ~80%.
 
 </div>
+
+## Contributing
+
+For information on contributing, please see [CONTRIBUTING.md](CONTRIBUTING.md).