Ensure that adding packages from scoped registries is handled in the "add" scripting

[Westbrook]

When attempting to add @spectrum-web-components/[email protected] via https://catalog.open-wc.org/add.html the following error message is returned:

{"errorMessage":"Could not index file","errorType":"Error","stackTrace":["a (/var/task/check-package-with-version.js:1:44023)","<anonymous>","process._tickDomainCallback (internal/process/next_tick.js:228:7)"]}

This is likely due to not handling the scoped registry appropriately.