Add helm3-dependency example demonstrating customization of OTS chart using Helm 3

helm3-dependency/Chart.yaml

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+apiVersion: v2
+name: wordpress
+description: Wordpress Argo demo
+type: application
+version: 0.1.0
+appVersion: 5.0.2
+
+dependencies:
+- name: wordpress
+  version: 5.0.2
+  repository: https://kubernetes-charts.storage.googleapis.com

helm3-dependency/README.md

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+# Helm 3 Dependencies
+
+This example application demonstrates how an OTS (off-the-shelf) helm chart can be retrieved and
+pinned to a specific helm sem version from an upstream helm repository, and customized using a custom
+values.yaml in the private git repository.
+
+In this example, the wordpress application is pulled from the stable helm repo, and pinned to v5.0.2:
+
+```yaml
+dependencies:
+- name: wordpress
+  version: 5.0.2
+  repository: https://kubernetes-charts.storage.googleapis.com
+```
+
+A custom values.yaml is used to customize the parameters of the wordpress helm chart:
+
+```yaml
+wordpress:
+  wordpressPassword: foo
+  mariadb:
+    db:
+      password: bar
+    rootUser:
+      password: baz
+```
+
+### Subchart Note
+
+The wordpress chart referenced in this example contains a subchart for mariadb as specified in the requirements.yaml file of the wordpress chart:
+```yaml
+- name: mariadb
+  version: 5.x.x
+  repository: https://kubernetes-charts.storage.googleapis.com/
+  condition: mariadb.enabled
+  tags:
+    - wordpress-database
+```
+
+In order to disable this chart, you must set the value to false for both `mariadb.enabled` and `wordpress.mariadb.enabled`. The first is used by the mariadb subchart condition field, the second is used by the wordpress chart deployment template. An example demonstration is available in the values-nomaria.yaml file:
+```yaml
+mariadb:
+  enabled: false
+
+wordpress:
+  wordpressPassword: foo
+  mariadb:
+    enabled: false
+  externalDatabase:
+    host: localhost
+    user: bn_wordpress
+    password: ""
+    database: bitnami_wordpress
+    port: 3306
+```

helm3-dependency/values-nomaria.yaml

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+mariadb:
+  enabled: false
+
+wordpress:
+  wordpressPassword: foo
+  mariadb:
+    enabled: false
+  externalDatabase:
+    host: localhost
+    user: bn_wordpress
+    password: ""
+    database: bitnami_wordpress
+    port: 3306

helm3-dependency/values.yaml

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+wordpress:
+  wordpressPassword: foo
+  mariadb:
+    db:
+      password: bar
+    rootUser:
+      password: baz