Added README.md for roles

Signed-off-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>

roles/kubernetes_argocd/README.md

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+# Ansible Role: ArgoCD
+
+This role installs and configures ArgoCD in a Kubernetes cluster.
+
+## Role Variables
+
+Available variables are listed below, along with default values (see `defaults/main.yml`):
+
+| Variable | Default | Description |
+|---|---|---|
+| `argocd_version` | `stable` | The version of ArgoCD to install. |
+| `argocd_namespace` | `argocd` | The namespace where ArgoCD will be installed. |
+| `argocd_repo` | `https://raw.githubusercontent.com/argoproj/argo-cd/refs/tags/{{ argocd_version }}/manifests/ha/install.yaml` | The URL to the ArgoCD installation manifests. |
+| `argocd_git_repository` | `https://github.com/argocd/argocd` | The Git repository URL for ArgoCD to use. |
+| `argocd_git_username` | `user` | The username for the Git repository. |
+| `argocd_git_pat` | `token` | The personal access token for the Git repository. |
+
+## Tasks
+
+The following tasks are performed by this role:
+
+- **Install ArgoCD**: Creates the ArgoCD namespace and applies the installation manifests.
+- **Apply ArgoCD Ingress**: Applies an Ingress resource for the ArgoCD server. **Note:** The template file `ingress.yml.j2` is missing from the role.
+- **Apply ArgoCD CM**: Applies a ConfigMap with command parameters for ArgoCD.
+- **Apply ArgoCD repository**: Creates a Secret with Git repository credentials.
+- **Apply ArgoCD Root Application**: Creates a root Application resource for ArgoCD.
+
+## Handlers
+
+There are no handlers in this role.
+
+## Usage
+
+Here is an example of how to use this role in a playbook:
+
+```yaml
+- hosts: kubernetes
+  roles:
+    - role: kubernetes_argocd
+      vars:
+        argocd_git_repository: "https://github.com/my-org/my-repo.git"
+        argocd_git_username: "my-user"
+        argocd_git_pat: "my-token"
+```