Run linters with GitHub actions

- for custom resources use yamllint since kubeval won't work
- for Kubernetes standard definitions use kubeval
- for charts use helm lint

.github/main.workflow

@@ -0,0 +1,21 @@
+workflow "Validate manifests" {
+  on = "push"
+  resolves = ["helm-lint"]
+}
+
+action "yaml-lint" {
+  uses = "stefanprodan/gh-actions/yamllint@master"
+  args = ["-d '{extends: relaxed, rules: {line-length: {max: 120}}}' -f parsable ./releases/*"]
+}
+
+action "kube-lint" {
+  needs = ["yaml-lint"]
+  uses = "stefanprodan/gh-actions/kubeval@master"
+  args = "workloads/*"
+}
+
+action "helm-lint" {
+  needs = ["yaml-lint"]
+  uses = "stefanprodan/gh-actions/helm@master"
+  args = ["lint charts/*"]
+}