ISSUE-132 ISSUE-141 Make resizable snackbars

[vyushin]

Fixed #132
Fixed #141

renderVariant

To most compatibility with current notistack versions i made renderVariant property of SnackbarProvider that can be default or wrapped.

Example:

<SnackbarProvider autoHideDuration={null}
                        renderVariant="wrapped"
                        anchorOrigin={{ vertical: 'bottom', horizontal: 'right' }}
                        dense={dense}>

        {children}
      </SnackbarProvider>

When renderVariant is wrapped snackbars will wrapped in container and snacks will resizible.
When renderVariant is default snackbars will works without this changes (like current version).

May be in future renderVariant might be deleted and notistack will has wrapped renderVariant by default.

[iamhosseindhv]

moved to #167