A new task page for assigining a pod to nodes using node affinity (#19265)

* Example for required node affinity tasks

Example for required node affinity tasks

* Create pod-nginx-preffered-affinity.yaml

* task for assigning pods nodes using node affinity

A new task for assigning pods nodes using node affinity

* Correcting syntax and spelling

Correcting syntax and spelling

* Correcting syntax and spelling

Correcting syntax and spelling

* fix for review comment 

Fix for review comment

* Adding min k8s server version

Adding min k8s server version

* Correcting small style issues

Correcting small style issues. This will also retrigger new build.

content/en/docs/tasks/configure-pod-container/assign-pods-nodes-using-node-affinity.md

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+---
+title: Assign Pods to Nodes using Node Affinity
+min-kubernetes-server-version: v1.10
+content_template: templates/task
+weight: 120
+---
+
+{{% capture overview %}}
+This page shows how to assign a Kubernetes Pod to a particular node using Node Affinity in a
+Kubernetes cluster.
+{{% /capture %}}
+
+{{% capture prerequisites %}}
+
+{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
+
+{{% /capture %}}
+
+{{% capture steps %}}
+
+## Add a label to a node
+
+1. List the nodes in your cluster, along with their labels:
+
+    ```shell
+    kubectl get nodes --show-labels
+    ```
+    The output is similar to this:
+
+    ```shell
+    NAME      STATUS    ROLES    AGE     VERSION        LABELS
+    worker0   Ready     <none>   1d      v1.13.0        ...,kubernetes.io/hostname=worker0
+    worker1   Ready     <none>   1d      v1.13.0        ...,kubernetes.io/hostname=worker1
+    worker2   Ready     <none>   1d      v1.13.0        ...,kubernetes.io/hostname=worker2
+    ```
+1. Chose one of your nodes, and add a label to it:
+
+    ```shell
+    kubectl label nodes <your-node-name> disktype=ssd
+    ```
+    where `<your-node-name>` is the name of your chosen node.
+
+1. Verify that your chosen node has a `disktype=ssd` label:
+
+    ```shell
+    kubectl get nodes --show-labels
+    ```
+
+    The output is similar to this:
+
+    ```
+    NAME      STATUS    ROLES    AGE     VERSION        LABELS
+    worker0   Ready     <none>   1d      v1.13.0        ...,disktype=ssd,kubernetes.io/hostname=worker0
+    worker1   Ready     <none>   1d      v1.13.0        ...,kubernetes.io/hostname=worker1
+    worker2   Ready     <none>   1d      v1.13.0        ...,kubernetes.io/hostname=worker2
+    ```
+
+    In the preceding output, you can see that the `worker0` node has a
+    `disktype=ssd` label.
+
+## Schedule a Pod using required node affinity
+
+This manifest describes a Pod that has a `requiredDuringSchedulingIgnoredDuringExecution` node affinity,`disktype: ssd`. 
+This means that the pod will get scheduled only on a node that has a `disktype=ssd` label. 
+
+{{< codenew file="pods/pod-nginx-required-affinity.yaml" >}}
+
+1. Apply the manifest to create a Pod that is scheduled onto your
+   chosen node:
+    
+    ```shell
+    kubectl apply -f https://k8s.io/examples/pods/pod-nginx-required-affinity.yaml
+    ```
+
+1. Verify that the pod is running on your chosen node:
+
+    ```shell
+    kubectl get pods --output=wide
+    ```
+
+    The output is similar to this:
+    
+    ```
+    NAME     READY     STATUS    RESTARTS   AGE    IP           NODE
+    nginx    1/1       Running   0          13s    10.200.0.4   worker0
+    ```
+    
+## Schedule a Pod using preferred node affinity
+
+This manifest describes a Pod that has a `preferredDuringSchedulingIgnoredDuringExecution` node affinity,`disktype: ssd`. 
+This means that the pod will prefer a node that has a `disktype=ssd` label. 
+
+{{< codenew file="pods/pod-nginx-preferred-affinity.yaml" >}}
+
+1. Apply the manifest to create a Pod that is scheduled onto your
+   chosen node:
+    
+    ```shell
+    kubectl apply -f https://k8s.io/examples/pods/pod-nginx-preferred-affinity.yaml
+    ```
+
+1. Verify that the pod is running on your chosen node:
+
+    ```shell
+    kubectl get pods --output=wide
+    ```
+
+    The output is similar to this:
+    
+    ```
+    NAME     READY     STATUS    RESTARTS   AGE    IP           NODE
+    nginx    1/1       Running   0          13s    10.200.0.4   worker0
+    ```
+
+{{% /capture %}}
+
+{{% capture whatsnext %}}
+Learn more about
+[Node Affinity](/docs/concepts/configuration/assign-pod-node/#node-affinity).
+{{% /capture %}}

content/en/examples/pods/pod-nginx-preferred-affinity.yaml

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+apiVersion: v1
+kind: Pod
+metadata:
+  name: nginx
+spec:
+  affinity:
+    nodeAffinity:
+      preferredDuringSchedulingIgnoredDuringExecution:
+      - weight: 1
+        preference:
+          matchExpressions:
+          - key: disktype
+            operator: In
+            values:
+            - ssd          
+  containers:
+  - name: nginx
+    image: nginx
+    imagePullPolicy: IfNotPresent

content/en/examples/pods/pod-nginx-required-affinity.yaml

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+apiVersion: v1
+kind: Pod
+metadata:
+  name: nginx
+spec:
+  affinity:
+    nodeAffinity:
+      requiredDuringSchedulingIgnoredDuringExecution:
+        nodeSelectorTerms:
+        - matchExpressions:
+          - key: disktype
+            operator: In
+            values:
+            - ssd            
+  containers:
+  - name: nginx
+    image: nginx
+    imagePullPolicy: IfNotPresent