feat: Helm chart contribution for argocd-notifications (#365)

* Helm chart contribution for argocd-notifications

The following chart is a contribution from work done at https://github.com/Bandwidth/ to facilitate installing https://github.com/argoproj-labs/argocd-notifications via Helm chart based on https://github.com/argoproj-labs/argocd-notifications/blob/master/manifests/install.yaml

charts/argocd-notifications/.helmignore

@@ -0,0 +1,22 @@
+# Patterns to ignore when building packages.
+# This supports shell glob matching, relative path matching, and
+# negation (prefixed with !). Only one pattern per line.
+.DS_Store
+# Common VCS dirs
+.git/
+.gitignore
+.bzr/
+.bzrignore
+.hg/
+.hgignore
+.svn/
+# Common backup files
+*.swp
+*.bak
+*.tmp
+*~
+# Various IDEs
+.project
+.idea/
+*.tmproj
+.vscode/