Parameterize artifact repository settings (#4)

* Parameterize artifact configuration

**What**
- Add parameterization of artifact store configuration

**Why**
Enables configuration of artifact repo secrets or omitting for use with IAM credentials

* Add workflow CRD definition to argo chart

**Why**
The workflow CRD must exist in order for argo to function

* artifactRepository values follow tree structure

* Deploy CRD as a pre-install hook

**What**
Using `lachlanevenson/k8s-kubectl`, which appears to be the most popular, off the shelf container with `kubectl` applied, run a job to apply the `workflow` crd.

**Why**
CRD is not, and cannot, be parameterized with release and so attempting to deploy as a regular template causes failures when installing subsequent releases.

charts/argo/templates/_workflow-crd.json

@@ -0,0 +1,19 @@
+{{- define "workflow-crd-json" }}
+{
+  "apiVersion": "apiextensions.k8s.io/v1beta1",
+  "kind": "CustomResourceDefinition",
+  "metadata": {
+    "name": "workflows.argoproj.io"
+  },
+  "spec": {
+    "group": "argoproj.io",
+    "names": {
+      "kind": "Workflow",
+      "plural": "workflows",
+      "shortNames": ["wf"]
+    },
+    "scope": "Namespaced",
+    "version": "v1alpha1"
+  }
+}
+{{- end}}