Redesign Developer Guide for Better Clarity and Onboarding

https://gateway.envoyproxy.io/contributions/develop/#prerequisites

Problem Statement
The current [Developer Guide](https://link-to-current-docs/) provides essential information but could be restructured for:

Better scannability (clear sections, bullet points, and visual hierarchy).

Reduced redundancy (e.g., repeated make commands).

New-user focus (prerequisites upfront, step-by-step workflows).

Proposed Redesign
Developer Guide
A streamlined guide to build, test, and deploy Envoy Gateway.
(Estimated: 5 min read)

1. Prerequisites
Must have:

Go (v1.24+) | [Install](https://go.dev/doc/install)

Make (v4.0+) | [Install](https://www.gnu.org/software/make)

Python 3 (with venv module)

Note: Debian/Ubuntu users may need python3-venv.

Optional:

Docker (v20.10.16+) | [Install](https://docs.docker.com/engine/install) (needed for image builds)

2. Quick Start
make help # List all available targets

3. Core Workflows
Building
make build # Build all binaries
make build BINS="envoy-gateway" # Build specific binary
Output: bin/// (e.g., bin/linux/amd64/).

Testing
make test # Run unit tests
make e2e # End-to-end tests
make testdata # Generate golden YAML files

Linting
make lint # Verify code style

4. Docker/Kubernetes Workflows
Image Management
IMAGE=docker.io/you/gateway-dev make image # Build image
IMAGE=docker.io/you/gateway-dev make push-multiarch # Push multi-arch image

Local Dev (Kind)
make create-cluster # Create Kind cluster
TAG=latest make kube-deploy # Deploy with latest image
IMAGE_PULL_POLICY=IfNotPresent make kube-deploy # Use custom image

Conformance Tests
TAG=latest make conformance # Run on Linux
# Mac workarounds: Use Docker Desktop or `make kube-deploy run-conformance`

5. Demo & Benchmarking
Demo Setup
make kube-demo # Deploy demo (Gateway + HTTPRoute)
make kube-demo-undeploy # Clean up

Benchmarking
make benchmark # Run performance tests (Nighthawk)
Reports: See benchmark_report.zip in release artifacts.