Added initial instructions file

Author: Roemer

.github/copilot-instructions.md

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+# Copilot Instructions for devcontainer-features
+
+## Project Overview
+- This repository provides reusable devcontainer features for Dev Containers.
+- Features are designed for cross-architecture (AMD64/ARM64) and cross-distro (Debian, Ubuntu, Alpine) compatibility.
+- Download URLs for binaries can be globally or per-feature overridden for corporate/cached environments.
+- Each feature is implemented as a self-contained directory under `features/src/<feature>/` with its own installer logic and documentation.
+- Each feature is implemented as a self-contained directory under `features/test/<feature>/` with its tests.
+
+## Key Components
+- `build.go`: Responsible for the overall build process, including generating the `README.md` files and managing the build lifecycle.
+- `features/src/<feature>/` — Source for each feature (e.g., go, node, docker-out, zig, git-lfs). Contains:
+  - `devcontainer-feature.json`: Feature metadata and options.
+  - `install.sh`, `installer.go`: Installation scripts and Go logic.
+  - `README.md`: Usage and configuration options. This file is automatically generated with the "Update-Readme-Files" task from build.go.
+- `features/test/<feature>/` — Tests for each feature. Contains:
+  - `scenarios.json`: File containing the different scenarios to test.
+  - `<scenarioname.sh>`: Verify script for each scenario
+  - `test-images.json`: File containing the test images to use.
+- `installer/` and `build/` — Shared Go utilities for downloading, extracting, and managing feature installation.
+- `override-all.env` — Example of all possible override environment variables for download URLs.
+- `README.md` — Documentation for the overall project and its features.
+
+## Developer Workflows
+- **Build**: Use Go to build/test feature logic. No monolithic build; each feature is self-contained.
+- **Testing**: Test scripts are in `features/test/<feature>/`. Use shell scripts for scenario-based testing.
+- **Overrides**: Set `DEV_FEATURE_OVERRIDE_LOCATION` to a file or URL for global download URL overrides. See `override-all.env` for supported keys.
+- **Version Resolution**: Features support both explicit and partial versioning. Set `versionResolve: true` to enable partial version resolution.
+
+## Project Conventions
+- Prefer explicit version pinning for reproducibility; partial versions require `versionResolve: true`.
+- Download URLs are split into `downloadUrlBase` and `downloadUrlPath` for flexibility with proxies/caches.
+- All features support ARM64 and AMD64 where possible; Alpine support is best-effort.
+- Use Go for core installer logic, with shell scripts for entrypoints.
+
+## Integration Points
+- Features can be used in any devcontainer by referencing the published image/tag.
+- Download and version resolution logic is centralized in Go utilities under `installer/`.
+- Global overrides are supported via environment variables or files (see `README.md`).
+
+## Examples
+- See `features/src/go/README.md` for Go feature usage and options.
+- See `features/src/docker-out/README.md` for Docker client integration.
+
+---
+
+For more, see the root `README.md` and each feature's `README.md`. When adding new features, follow the structure and conventions above.