ci: Add Copilot setup steps (#892)

Based on
https://docs.github.com/en/copilot/how-tos/use-copilot-agents/coding-agent/customize-the-agent-environment

## Description
This PR adds the GitHub workflow for Copilot agent sessions

## Related Issue
N/A

## Type of Change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Documentation update
- [ ] Code refactoring
- [X] Other (please describe): Workflow

## Checklist

- [X] I have read the [CONTRIBUTING](CONTRIBUTING.md) guidelines
- [X] My code follows the code style of this project
- [X] I have added tests that prove my fix is effective or that my
feature works
- [X] All new and existing tests pass
- [X] I have updated the documentation accordingly
- [X] My changes generate no new warnings

## Additional Notes

Author: DannyvdSluijs

.github/workflows/copilot-setup-steps.yml

@@ -0,0 +1,41 @@
+name: "Copilot Setup Steps"
+
+# Automatically run the setup steps when they are changed to allow for easy validation, and
+# allow manual testing through the repository's "Actions" tab
+on:
+    workflow_dispatch:
+    push:
+        paths:
+            - .github/workflows/copilot-setup-steps.yml
+    pull_request:
+        paths:
+            - .github/workflows/copilot-setup-steps.yml
+
+jobs:
+    # The job MUST be called `copilot-setup-steps` or it will not be picked up by Copilot.
+    copilot-setup-steps:
+        runs-on: ubuntu-latest
+
+        # Set the permissions to the lowest permissions possible needed for your steps.
+        # Copilot will be given its own token for its operations.
+        permissions:
+            # If you want to clone the repository as part of your setup steps, for example to install dependencies, you'll need the `contents: read` permission. If you don't clone the repository in your setup steps, Copilot will do this for you automatically after the steps complete.
+            contents: read
+
+        # You can define any steps you want, and they will run before the agent starts.
+        # If you do not check out your code, Copilot will do this for you.
+        steps:
+            - name: Checkout code
+              uses: actions/checkout@v5
+
+            - name: "Install PHP"
+              uses: "shivammathur/setup-php@v2"
+              with:
+                coverage: "none"
+                extensions: "intl, zip"
+                ini-values: "memory_limit=-1, phar.readonly=0, error_reporting=E_ALL, display_errors=On"
+                php-version: "7.2"
+                tools: composer
+
+            - name: "Install dependencies"
+              run: "composer install"