docs: add CONTRIBUTING.md with development and contribution guidelines

CONTRIBUTING.md

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+# Contributing to JWS Operator
+
+Thanks for your interest in contributing to `jws-operator`.
+
+This guide focuses on the contributor workflow for this repository. For product-level usage and deployment details, see `README.md`.
+
+## Prerequisites
+
+Required:
+
+- Go (see `go.mod` for version used by the project)
+- `make`
+- `kubectl`
+
+Depending on your task:
+
+- `docker` or `podman` (for image builds)
+- `oc` (for OpenShift-specific workflows and e2e setup)
+- `kind` (for `make test-e2e`)
+
+Most development tools used by the build (`controller-gen`, `setup-envtest`, `golangci-lint`, `kustomize`) are bootstrapped by `make` targets into `bin/`.
+
+## Local Setup
+
+```bash
+git clone https://github.com/web-servers/jws-operator.git
+cd jws-operator
+make help
+```
+
+`make help` shows the supported targets and is the best entry point before running other commands.
+
+## Build
+
+Build the manager binary:
+
+```bash
+make build
+```
+
+This generates manifests/code, runs `fmt` and `vet`, and builds `bin/manager`.
+
+Build and push an image:
+
+```bash
+export IMG=quay.io/<your-user>/jws-operator:latest
+make docker-build docker-push
+```
+
+If you use Podman:
+
+```bash
+make docker-build docker-push CONTAINER_TOOL=podman
+```
+
+## Tests
+
+### Unit tests
+
+```bash
+make test
+```
+
+This target sets up envtest assets automatically (`make setup-envtest`) and runs all non-e2e Go tests.
+
+### E2E tests on Kind
+
+```bash
+make test-e2e
+```
+
+This creates a Kind cluster (if missing), deploys the operator, runs e2e tests, then cleans up.
+
+### E2E tests on a real cluster
+
+```bash
+make test-e2e-real
+```
+
+Common variables:
+
+- `NAMESPACE_FOR_TESTING` (default: `jws-operator-tests`)
+- `TEST_IMG` (default: `quay.io/web-servers/tomcat10:latest`)
+- `EXECUTE_TEST` (default: `WebServerControllerTest`)
+- `TEST_PARAM` (extra ginkgo flags)
+
+Example:
+
+```bash
+make test-e2e-real EXECUTE_TEST=BasicTest
+```
+
+Real-cluster prerequisites (secrets/storage) are documented in `README.md` and `test-scripts/README.md`.
+
+## Linting and Formatting
+
+```bash
+make lint
+make lint-fix
+make lint-config
+```
+
+For formatting only:
+
+```bash
+make fmt
+```
+
+## Pull Request Workflow
+
+1. Fork the repository and create a branch from `main`.
+2. Make focused changes with clear commit messages.
+3. Run relevant checks locally (`make build`, `make lint`, `make test`, and e2e where applicable).
+4. Open a PR against `web-servers/jws-operator:main`.
+5. Link related issues in the PR description (for example, `Fixes #123`).
+
+## Reporting Issues and Getting Help
+
+- Use [GitHub Issues](https://github.com/web-servers/jws-operator/issues) for bugs and feature requests.
+- For project context and runtime usage, refer to `README.md`.