feat: allow custom priconfig

[Agritite]

Allow user-provided priconfig.xml just like appxmanifest.xml.

A default priconfig.xml generated by makepri createconfig simply exports every single file in the package, recursively. Also because <autoResourcePackage qualifier="Language"/> is set, makepri automatically creates resources.language-xx.pri for every language even when you don't use any language specific resources. This is most likely undesired, and users would instead want to provide their own priconfig.xml.

The new PackagingOptions parameters are designed to not affect current behavior. If you would prefer a different schema let me know.

One minor difference is that the original code path of makepri createconfig creates the config directly in the package directory, and thus will be packaged into the msix. In this implementation when users provide a custom priconfig.xml it will not be copied into the package directory. I'm not sure whether this is worth mentioning in README, or should add as an option, because you don't need to ship the priconfig.xml, only the resources.pri.