invoice-ninja: Deploy Invoice Ninja

Invoice Ninja is a small business management tool.  Tabitha wants to
use it for HLC.

I am a bit concerned about the code quality of this application, and
definitely alarmed at the data it send upstream, so I have tried to be
extra careful with it.  All privileges are revoked, including access to
the Internet.

argocd/applications/invoice-ninja.yaml

@@ -0,0 +1,13 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: invoice-ninja
+  namespace: argocd
+spec:
+  destination:
+    server: https://kubernetes.default.svc
+  project: default
+  source:
+    path: invoice-ninja
+    repoURL: https://git.pyrocufflink.blue/infra/kubernetes.git
+    targetRevision: master