Missing zstd runtime dependency on Windows

[certik]

lfortran does not run on Windows out of the box (we get a Windows dialog box that zstd.dll cannot be found). One must first do conda install zstd, then it works. The following version fixed it:

    package                    |            build
    ---------------------------|-----------------
    zstd-1.5.6                 |       h0ea2cb4_0         341 KB  conda-forge
    ------------------------------------------------------------
                                           Total:         341 KB