feat: add custom policy example (HPA_best_practices) (#321)

examples/HPA_best_practices/Fail.yaml

+apiVersion: autoscaling/v1
+kind: HorizontalPodAutoscaler
+metadata:
+  name: php-apache
+spec:
+  scaleTargetRef:
+    apiVersion: apps/v1
+    kind: Deployment
+    name: php-apache
+  minReplicas: 1
+  maxReplicas: 10
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examples/HPA_best_practices/README.md

+# Policy: HPA_best_practices 
+When auto-scaling resource utilization is triggered with HPA (HorizontalPodAutoscaler), a `targetCPUUtilizationPercentage` should be defined in Manifest File to get a Threshold CPU Limit and it will Scale a Pod and Create a New Replica
+## Ensure targetCPUUtilizationPercentage is Set
+ Having an `targetCPUUtilizationPercentage` is Useful to create Replicas Based on CPU_Utilization
+### When this rule is failing? 
+If `targetCPUUtilizationPercentage` is not found in Manifest file of `Kind: HorizontalPodAutoscaler`
+```
+apiVersion: autoscaling/v1
+kind: HorizontalPodAutoscaler
+metadata:
+  name: php-apache
+spec:
+  scaleTargetRef:
+    apiVersion: apps/v1
+    kind: Deployment
+    name: php-apache
+  minReplicas: 1
+  maxReplicas: 10
+```
+## Policy author
+Avinash \\ [Avinash](https://github.com/Avinashnayak27)
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examples/HPA_best_practices/pass.yaml

+apiVersion: autoscaling/v1
+kind: HorizontalPodAutoscaler
+metadata:
+  name: php-apache
+spec:
+  scaleTargetRef:
+    apiVersion: apps/v1
+    kind: Deployment
+    name: php-apache
+  minReplicas: 1
+  maxReplicas: 10
+  targetCPUUtilizationPercentage: 80
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examples/HPA_best_practices/policy.yaml

+apiVersion: v1
+policies:
+  - name: Default
+    isDefault: true
+    rules:
+    - identifier: HPA_MISSING_targetCPUUtilizationPercentage
+      messageOnFailure: Missing targetCPUUtilizationPercentage - value should be in Percentage  
+   customRules:
+     - identifier: HPA_MISSING_targetCPUUtilizationPercentage
+       name: Ensure HPA Has targetCPUUtilizationPercentage
+       defaultMessageOnFailure: Missing targetCPUUtilizationPercentage - value should be in Percentage
+       schema:
+        properties:
+          kind:
+           enum:
+            - HorizontalPodAutoscaler
+          spec:
+            type: object
+            properties:
+              targetCPUUtilizationPercentage:
+                type: integer
+            required:
+            - targetCPUUtilizationPercentage
+        required:
+          - kind
+          - spec
+ 
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