add doc gen template and update doc for Ingress

[M00nF1sh]

Add doc gen template & update doc for Ingress
Note, the doc gen tool don't support kubebuilder v2.
You need to

1. create a doc.go with contents below

// Package v1beta2 contains API Schema definitions for the appmesh v1beta2 API group
// +kubebuilder:object:generate=true
// +groupName=appmesh.k8s.aws
package v1beta2

2. add // +genclient to type declarations with a blank line before other comments.
3. generate doc with gen-crd-api-reference-docs -template-dir=/Users/yyyng/workplace/AppMesh/aws-app-mesh-controller-for-k8s/hack/api-docs/template/ -config=/Users/yyyng/workplace/AppMesh/aws-app-mesh-controller-for-k8s/hack/api-docs/config.json -api-dir=github.com/aws/aws-app-mesh-controller-for-k8s/apis/appmesh/v1beta2 -out-file docs/reference/api_spec.md

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[fawadkhaliq]

awesome!

[fawadkhaliq]

/lgtm