chore: add contributing guidelines (#556)

* chore: add contributing guidelines

Signed-off-by: Carlo Minotti <50220438+minottic@users.noreply.github.com>

* Align contributing guidelines with commitlint

Signed-off-by: Carlo Minotti <50220438+minottic@users.noreply.github.com>

---------

Signed-off-by: Carlo Minotti <50220438+minottic@users.noreply.github.com>

Author: minottic

.github/CONTRIBUTING.md

@@ -0,0 +1,44 @@
+# Contributing to SciLog
+
+Thank you for considering contributing to SciLog! By contributing, you agree to follow our contribution guidelines.
+
+## 1. Code of Conduct
+
+Please adhere to the [Code of Conduct](./CODE_OF_CONDUCT.md) in all interactions with the project.
+
+## 2. How to Contribute
+
+You can contribute by:
+
+- Reporting bugs
+- Suggesting improvements or new features
+- Submitting Pull Requests
+
+## 3. Pull Requests
+
+- All contributions must be made via **pull requests (PRs)**.
+- PRs can come either from a **fork** of the repository or from a **branch** within this repository.
+- PRs are expected to be **atomic**—each PR should contain only one logical change.
+- **Codeowners** will automatically be added as reviewers.
+- You may add any additional reviewers if needed.
+- Make sure to address any comments before merging.
+- **Continuous Integration (CI) must pass** before a PR can be merged.
+- PRs will be **squashed and merged**.
+- The squashed commit should follow **Conventional Commit style**. See here the
+  [specification](https://www.conventionalcommits.org/en/v1.0.0/).
+- Include a 'why' in the commit body to document the rationale behind the change. 
+This provides essential context for future maintenance and helps others understand the project's growth.
+- By default, the PR title serves as the commit’s subject line, while the PR description populates
+the commit body.
+
+## 4. Additional Guidelines
+
+- Ensure your changes include **documentation updates** when relevant.
+- Follow **existing code style and patterns** in the project.
+- Keep PRs **focused and concise** to make reviewing easier.
+
+## 5. Reporting Issues or Security Concerns
+
+- For **security issues**, please follow the instructions in [SECURITY.md](./SECURITY.md).
+- For other issues or feature requests, use the
+  [GitHub Issues page](https://github.com/paulscherrerinstitute/scilog/issues).