Fix docs deployment

[visr]

@asinghvi17 I see the URLs from #17 404. The CI action fails with:

[Documentation: ../../../.julia/packages/Documenter/Bs999/src/html/HTMLWriter.jl#L742](https://github.com/JuliaGeo/NaturalEarth.jl/pull/17/files#annotation_31566795895)
Unable to determine the repository root URL for the navbar link.
This can happen when a string is passed to the `repo` keyword of `makedocs`.

To remove this warning, either pass a Remotes.Remote object to `repo` to completely
specify the remote repository, or explicitly set the remote URL by setting `repolink`
via `makedocs(format = HTML(repolink = "..."), ...)`.

Also I guess we should use https://juliageo.org/NaturalEarth.jl/ as the canonical URL rather than juliageo.github.io which redirects there?