add maintainer review action to main.workflow

.github/main.workflow

+workflow "New workflow" {
+  on = "pull_request"
+  resolves = [".github/actions/add-maintainers-as-reviewers"]
+}
+
+action ".github/actions/add-maintainers-as-reviewers" {
+  uses = ".github/actions/add-maintainers-as-reviewers"
+  secrets = ["GITHUB_TOKEN"]
+}