docs: add K3s integration guide for Kubernetes deployment

[nailo2c]

Explanation

Add a new documentation page for deploying WasmEdge applications on K3s.

I've run the commands in this doc on GCP GCE Ubuntu 24.04 LTS x86_64, and they work well.

• wasmedge/example-wasi

• http-server

Related issue

Closes WasmEdge/WasmEdge#2132

What type of PR is this

/kind documentation

Proposed Changes

• Add docs/develop/deploy/kubernetes/k3s.md covering:
  • Installing WasmEdge and the containerd-shim-wasmedge (pre-built binary or build from source)
  • Installing K3s with automatic WasmEdge RuntimeClass detection
  • Running a simple WebAssembly app (wasi-demo)
  • Running a WebAssembly-based HTTP service using Deployment + NodePort Service
• All steps have been verified on an x86_64 Ubuntu 24.04 GCE instance

[hydai]

Thanks.