Add dataverse support

[noamross]

[larsvilhuber]

+1 https://cran.r-project.org/package=dataverse

[mpadge]

Thanks @larsvilhuber. Development of this package has been temporarily paused, but will hopefully resume in the near future (pending funding decisions ... 🤞 )

[larsvilhuber]

@mpadge kind of what the data (commit dates) suggested. Thanks.