Add devcontainer for codespaces

[npolshakova]

Description

Adding a devcontainer similar to Istio's setup: https://github.com/istio/istio/blob/master/.devcontainer/devcontainer.json This will make it easier to run our ContribFest workshop at KubeCon.

Fixes: #13487

Change Type

/kind documentation

Changelog

NONE

Additional Notes

Run make build-tools-image locally to test the image build. Currently, the devcontainers will build the image when the Codespace starts. Once we've iterated on the build image, we should publish it on releases and pin it in the devcontainer like Istio does:

  "image": "gcr.io/istio-testing/build-tools:master-116bd1273dfc5d27136461597f5ff54f535f416b",

Why codespaces?
All personal (individual) GitHub.com accounts include a quota of free usage each month. GitHub will provide users in the free plan 120 core hours or 60 hours of run time on a 2 core codespace, plus 15 GB of storage each month. See: https://github.com/features/codespaces This should be enough to run the contribfest workshop.

Example run in Codespace:

build-tools:/workspaces/kgateway# 
build-tools:/workspaces/kgateway# go version
go version go1.25.6 linux/amd64
build-tools:/workspaces/kgateway# rustc --version
rustc 1.86.0 (05f9846f8 2025-03-31)
build-tools:/workspaces/kgateway# make generate-all

[Copilot]

Pull request overview

This PR adds a devcontainer configuration to enable GitHub Codespaces for a ContribFest workshop at KubeCon. The setup is inspired by Istio's approach and includes a custom build-tools Docker image with development dependencies.

Changes:

• Added a build-tools Docker image with Go, Rust, and common development tools for Codespaces
• Created devcontainer configuration to enable GitHub Codespaces support
• Added GitHub Actions workflow to build and publish the build-tools image to GHCR

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
tools/build-tools/Dockerfile	Defines the build-tools image with development dependencies
tools/build-tools/docker-entrypoint.sh	Entrypoint script for handling credentials and permissions
tools/build-tools/prow-entrypoint.sh	Minimal entrypoint for CI environments with dockerd
tools/build-tools/bashrc	Custom bash configuration with prompt and make completion
tools/build-tools/README.md	Documentation for the build-tools image
.devcontainer/devcontainer.json	Devcontainer configuration for Codespaces
.github/workflows/build-tools.yaml	CI workflow to build and publish the image
Makefile	Added targets to build the build-tools image locally

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.