Add the Helm Repository for VAST Block CSI Driver

Add the Helm repository that contains the VAST Block CSI Driver Helm chart to the list of available repositories:

Add the Helm repository for VAST Block CSI Driver:
```
helm repo add <repo> https://vast-data.github.io/vast-csi
```
Specify any suitable name for repo. This name will be used to refer to the VAST Block CSI Driver repository when running Helm commands. For example: vastblock
Verify that the repository has been added:
```
helm repo list
```
The output is similar to the following:
```
NAME      URL 
vastblock https://vast-data.github.io/vast-csi
```