[FEATURE] Add a variable related with fromBackup to helm chart of longhorn.

[Bok ki Ryu]

Is your feature request related to a problem? Please describe (👍 if you like this request)

Add a variable related with fromBackup to helm chart of longhorn.

Describe the solution you'd like

It would be nice to add a value to Helm chart values that can modify the "fromBackup" of the longhorn storage class.

Describe alternatives you've considered

Additional context

[Derek Su]

@bkkoli

It would be nice to add a value to Helm chart values that can modify the "fromBackup" of the longhorn storage class.

Do you mean newly created stroage classes or the default longhorn storage class?