Add documentation for the new antctl check commands (antrea-io#6373)

Signed-off-by: Kanha gupta <[email protected]>

docs/antctl.md

@@ -21,6 +21,9 @@ running in three different modes:
 - [Usage](#usage)
   - [Showing or changing log verbosity level](#showing-or-changing-log-verbosity-level)
   - [Showing feature gates status](#showing-feature-gates-status)
+  - [Performing checks to facilitate installation process](#performing-checks-to-facilitate-installation-process)
+    - [Pre-installation checks](#pre-installation-checks)
+    - [Post-installation checks](#post-installation-checks)
   - [Collecting support information](#collecting-support-information)
   - [controllerinfo and agentinfo commands](#controllerinfo-and-agentinfo-commands)
   - [NetworkPolicy commands](#networkpolicy-commands)
@@ -125,6 +128,52 @@ The following command prints the current feature gates:
 antctl get featuregates
 ```
 
+### Performing checks to facilitate installation process
+
+Antrea provides a utility command `antctl check` designed to perform checks
+that verify whether a Kubernetes cluster is correctly configured for installing
+Antrea, and also to confirm that Antrea has been installed correctly.
+
+#### Pre-installation checks
+
+Before installing Antrea, it can be helpful to ensure that the Kubernetes
+cluster is configured properly. This can prevent potential issues that might
+arise during the installation of Antrea. To perform these pre-installation
+checks, simply run the command as follows:
+
+```bash
+antctl check cluster
+```
+
+Run the following command to discover more options:
+
+```bash
+antctl check cluster --help
+```
+
+#### Post-installation checks
+
+Once Antrea is installed, you can verify that networking is functioning
+correctly within your cluster. To perform post-installation checks, simply run
+the command as follows:
+
+```bash
+antctl check installation
+```
+
+In case Antrea is installed in a custom namespace, You
+can specify the namespace by adding the flag:
+
+```bash
+antctl check installation --namespace [NAMESPACE]
+```
+
+Run the following command to discover more options:
+
+```bash
+antctl check installation --help
+```
+
 ### Collecting support information
 
 Starting with version 0.7.0, Antrea supports the `antctl supportbundle` command,