Add the Helm Repository for VAST COSI Driver

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

Add the Helm repository for VAST COSI 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 COS Driver repository when running Helm commands. For example: vastcosi
Verify that the repository has been added:
```
helm repo list
```
The output is similar to the following:
```
NAME     URL 
vastcosi https://vast-data.github.io/vast-csi
```