feat(helm): allow to customize init image (#18649)

* feat(helm): allow to customize init image

* chore(helm): bump chart version to 0.5.8

helm/superset/values.schema.json

@@ -111,6 +111,26 @@
         "imagePullSecrets": {
             "type": "array"
         },
+        "initImage": {
+            "type": "object",
+            "additionalProperties": false,
+            "properties": {
+                "repository": {
+                    "type": "string"
+                },
+                "tag": {
+                    "type": "string"
+                },
+                "pullPolicy": {
+                    "$ref": "https://raw.githubusercontent.com/yannh/kubernetes-json-schema/master/v1.23.0/_definitions.json##/definitions/io.k8s.api.core.v1.Container/properties/imagePullPolicy"
+                }
+            },
+            "required": [
+                "repository",
+                "tag",
+                "pullPolicy"
+            ]
+        },
         "service": {
             "type": "object",
             "additionalProperties": false,