chore: add contributing guidelines to improve collaboration

Author: konradmichalik

CONTRIBUTING.md

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+# Contributing
+
+Thank you for considering contributing to this project! Every contribution is welcome and helps improve the quality of the project. To ensure a smooth process and maintain high code quality, please follow the steps below.
+
+## Requirements
+
+- [DDEV](https://ddev.readthedocs.io/en/stable/)
+
+## Preparation
+
+```bash
+# Clone repository
+git clone https://github.com/xima-media/xima-typo3-internal-news.git
+cd xima-typo3-internal-news
+
+# Start the project with DDEV
+ddev start
+
+# Install dependencies
+ddev composer install
+```
+
+## Run linters
+
+```bash
+# All linters
+ddev composer lint
+
+# Specific linters
+ddev composer lint:composer
+ddev composer lint:editorconfig
+ddev composer lint:language
+ddev composer lint:php
+ddev composer lint:typoscript
+ddev composer lint:yaml
+
+# Fix all CGL issues
+ddev composer fix
+
+# Fix specific CGL issues
+ddev composer fix:composer
+ddev composer fix:editorconfig
+ddev composer fix:php
+```
+
+## Run static code analysis
+
+```bash
+# All static code analyzers
+ddev composer sca
+
+# Specific static code analyzers
+ddev composer sca:php
+```
+
+## TYPO3 Setup
+
+For testing the extension, you need to set up the TYPO3 instances.
+
+```bash
+# Install all TYPO3 versions, which are supported by the extension
+ddev install all
+
+# Or install specific TYPO3 versions
+ddev install 12
+ddev install 13
+
+# Open the overview page
+ddev launch
+
+# Run TYPO3 specific commands
+ddev 12 typo3 cache:flush
+ddev 13 composer install
+ddev all typo3 database:updateschema
+```
+
+## Submit a pull request
+
+After completing your work, **open a pull request** and provide a description of your changes. Ideally, your PR should reference an issue that explains the problem you are addressing.
+
+All mentioned code quality tools will run automatically on every pull request. For more details, see the relevant [workflows][1].
+
+[1]: .github/workflows