Adding README

Adding a Readme file for main repo page info.

Story: 2007360
Task: 39222

Change-Id: Ic5be5e1b268691eb07676f0d899b3c2faf3c7b04
Signed-off-by: Sabeel Ansari <Sabeel.Ansari@windriver.com>

README.rst

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+# StarlingX/Cert-Manager-Armada-App
+
+## Introduction
+[Cert-Manager](https://cert-manager.io/) is Kubernetes native application that facilities certificate management. This repository deploys Cert-Manager as a platform-managed application using Armada Helm Charts for the StarlingX project.
+
+## Build
+The build tools available as indepdendent repositories under the StarlingX project are necessary to build this  Armada chart.
+
+See [StarlingX Build Guide](https://docs.starlingx.io/developer_resources/build_guide.html) for more details.
+
+To build this app:
+```
+${MY_REPO_ROOT_DIR}/cgcs-root/build-tools/build-pkgs cert-manager-helm stx-cert-manager-helm
+```
+The generated RPM is located in `$MY_BUILD_DIR/std/rpmbuild/RPMS`.
+
+To extract the tarball without installing on build system, use command:
+```
+rpm2cpio stx-cert-manager-helm-1.0-0.tis.noarch.rpm | cpio -idmv
+```
+
+## Usage
+Note that the Cert-Manager application is included on a StarlingX install system by default.
+
+Following commands can be used to upload, apply, remove, delete, and view the application:
+
+```
+system application-remove cert-manager
+system application-delete cert-manager
+system application-upload <.tgz file>
+system application-apply cert-manager
+system application-list
+```
+
+Cert-Manager Kubernetes resources can be found in the `cert-manager` namespace.
+
+```
+kubectl get namespaces | grep cert-manager
+kubectl get crd | grep cert-manager
+kubectl get pods --namespace cert-manager
+```