Adds code to expose the ipk configuration values and registers the ipk
package format with nfpm.
Updates the documentation with how to use the new ipk specific
configuration parameters.
**This isn't ready to merge, but I have some questions**
1. I copied the `TestIPKSpecificConfig()`
([code](https://github.com/goreleaser/goreleaser/compare/main...schmidtw:goreleaser:main#diff-912a4af69daf4d89537b6bea43a1b7fe65683128ea1be66d6ec77046c76d064dR1358))
from the `TestAPKSpecificConfig()` and found it only is really testing
if specific scripts are there or not. Since IPK doesn't have any
additional scripts, just fields in one file do I need this test
function? Is there a better way to validate the output?
2. I have run into issues where the tests expect `goreleaser` to be the
org & repo - is there a way to override this in my fork without changing
the code?
3. Is the `ToNFPAlts()` and `ToNFP()` living in the config.go file ok?
There wasn't much code in that file, so I figured I'd ask if you'd
rather this code be elsewhere.
---------
Co-authored-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>
cc114fc8b9