docs: adds documentation for Windows install (#3)

Co-authored-by: Leonardo Cecchi <leonardo.cecchi@enterprisedb.com>
Co-authored-by: Armando Ruocco <armando.ruocco@enterprisedb.com>

Author: 3 people

README.md

@@ -6,6 +6,8 @@ an OpenShift environment.
 
 For details, please refer to Cloud Native PostgreSQL documentation.
 
+## Mac OS and Linux install
+
 You can install the plugin in your system with:
 
 ``` sh
@@ -16,3 +18,38 @@ curl -sSfL \
 
 The plugin requires the Cloud Native PostgreSQL operator to be
 installed in the Kubernetes/Openshift cluster.
+
+## Windows install
+
+To install the plugin on Windows go to the [releases
+page](https://github.com/EnterpriseDB/kubectl-cnp/releases) and get the most
+recent release for your Windows architecture.
+
+For example, if you are using an `x86_64` build of Windows, you would download
+the file named `kubectl-cnp_<version>_windows_x86_64.tar.gz`.
+
+The release includes a checksum file, named
+`kubectl-cnp-<version>-checksums.txt`, that can be used to validate the
+integrity of the Kubectl binary.
+
+To validate the file you can compare the output of the following command
+against the relative line in the checksums file:
+
+```
+CertUtil -hashfile <tar-file> SHA256
+```
+
+Now you can extract the contents of the TAR archive using the following
+command:
+
+```
+tar xvzf <tar-file>
+```
+
+You can copy the `kubectl-cnp.exe` file in any directory pointed by your `PATH`
+environment variable, or prepend or append the Kubectl Cnp binary folder to
+your `PATH` environment variable.
+
+The directory where `kubectl.exe` is is usually a good choice for copying the
+`kubectl-cnp.exe` file to.
+