nnz and indtype for ReadOnly?

[orenbenkiki]

The code seems to be missing these:

function SparseArrays.indtype(read_only::SparseArrays.ReadOnly)::Type
    return SparseArrays.indtype(parent(read_only))
end

function SparseArrays.nnz(read_only::SparseArrays.ReadOnly)::Integer
    return SparseArrays.nnz(parent(read_only))
end

Any reason they shouldn't exist?

[ViralBShah]

I believe these should be ok to have.