Add Windows Contributor Onboarding Guide

Community & Support: [LinkedIn Group](https://www.linkedin.com/groups/14656108/) · [Slack #project-nest](https://owasp.slack.com/archives/project-nest)

Active project leaders: Arkadii Yakovets -- [GitHub](https://github.com/arkid15r/) · [LinkedIn](https://www.linkedin.com/in/arkid15r/) · [Slack](https://owasp.slack.com/team/U060W3NKLTF); Kate Golovanova -- [GitHub](https://github.com/kasya/) · [LinkedIn](https://www.linkedin.com/in/kate-golovanova/) · [Slack](https://owasp.slack.com/team/U07PWB1JZ6Z)

[Contributing](https://github.com/owasp/nest/blob/main/CONTRIBUTING.md) · [Code of Conduct](https://github.com/owasp/nest/blob/main/CODE_OF_CONDUCT.md) · [GSoC Mentors](https://github.com/owasp/nest/blob/main/MENTORS.md)

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**Is your feature request related to a problem? Please describe.**
Currently, the repository lacks a step-by-step onboarding guide for contributors using Windows environments. Most instructions assume Linux/macOS setups, which can create friction for new contributors.

**Describe the solution you'd like**
Create a dedicated Windows setup guide in docs/ (or CONTRIBUTING.md).

Include steps for:

Installing prerequisites (Node.js, Docker, Git, etc.)

Handling common errors (path issues, Docker permissions, etc.)

Running tests and linting locally on Windows.

Add troubleshooting tips for frequent problems (e.g., dependency installation failures, environment variables).

**Are you going to work on implementing this?**

- [x] Yes
- [ ] No

**Additional context**
Makes the project more inclusive for Windows developers.

Reduces repeated queries in discussions/issues.

Improves contributor experience and accelerates onboarding.

Start by reading the existing CONTRIBUTING.md and inspecting docs/ to identify the current setup, test, and linting guidance. Add a Windows-focused guide covering Node.js, Docker, and Git prerequisites, common path and permission errors, dependency and environment-variable troubleshooting, and local tests and linting. Done means a Windows contributor can follow the guide from setup through validation without relying on Linux or macOS instructions.

Written by the indexing model from the issue text.