[FEATURE] make the "listing" string configurable

[Matthew Herber]

package-list-action/PackageBuilder/Build.cs

Line 87 in a3c757b

 name = $"{manifest.displayName} Listing", 

Id love for this string to be configurable so I can make it more specific to my project. in my case I want to change it to something like "system" or "library" instead of "listing", but I cant do that unless I fork and use a custom version right now