bug with .tar.gz upload - name needs .tar.gz in it

[vsoch]

There is a bug with the title that, given it does not have .tar.gz with the oras-go client, it will not be extracted as such.

[MichaelKopfMkf]

I think this is not the desired behaviour.
The oras cli does not publish directories with a tar.gz file ending in the title.

I think it uses the layers annotation io.deis.oras.content.unpack to decide whether to unpack a layer or not.
the title is then used as target location for the unpacked tar.

I suggested to make oras-py also use this annotation here:
#170