* guix/import/nuget.scm: New file.
* guix/scripts/import/nuget.scm: New file.
* guix/scripts/import.scm: Add reference to it.
* gnu/packages/guile-xyz.scm (guile-semver): Update to 0.2.0.
[source]: Switch.
Change-Id: I159c5cf3b02b42435b03d989d5815d3fcf001c92