Added ignore missing package name to get-packages

[tzdesign]

Hi there,

we are also working with changesets, but in our current project there are packages that generate package.json files within the build process that do not have a name.

These files are used for module types like:

{
  "type": "module"
}

Unfortunately there is no way to ignore them, neither with you nor with changesets. I thought I'd do a PR, let me know if there's anything else I should change here.

When you release a new version, I will also make a PR in changesets project, so that you can pass on the value via the config.

Thanks in advance