issue #85: Split and expand project documentation

CONTRIBUTING.md

@@ -0,0 +1,69 @@
+# Contributing
+
+Thanks for your interest in contributing to `treels`.
+
+## Getting started
+
+```bash
+git clone https://github.com/OussamaM1/treels.git
+cd treels
+go test ./...
+```
+
+## Development workflow
+
+Before opening a pull request, run:
+
+```bash
+go test ./...
+go vet ./...
+golangci-lint run
+```
+
+If you do not have `golangci-lint` installed, CI will still run it on the pull request.
+
+## Contribution guidelines
+
+- Keep changes focused and easy to review.
+- Add or update tests for behavior changes.
+- Update documentation for user-facing changes.
+- Prefer existing project patterns before adding new abstractions.
+- Avoid introducing new dependencies unless they are clearly justified.
+
+## Adding or changing CLI behavior
+
+For a new flag or output behavior, update:
+
+- `cmd/flag.go`
+- `module/types.go`
+- relevant implementation under `service/`
+- tests under `cmd/` and/or `service/`
+- `README.md`
+- relevant files under `docs/`
+
+## Documentation style
+
+- Prefer examples using `--no-icons` unless documenting icon behavior.
+- Keep README concise and link to detailed docs.
+- Document flag interactions when behavior may be surprising.
+- Be explicit about limitations, especially for `.gitignore` and JSON output.
+
+## Reporting bugs
+
+When reporting a bug, include:
+
+- operating system
+- `treels --version`
+- command used
+- expected output
+- actual output
+- small reproduction directory structure, if possible
+
+## Feature requests
+
+Good feature requests explain:
+
+- the problem or workflow
+- proposed CLI usage
+- expected output
+- any interaction with existing flags