Suggest changing the default output directory

[willhains]

...to ${project.build.directory}/generated-sources/package-info, since this is where Maven and IDEs expect generated sources to be.

[willhains]

@bohnman I have submitted a PR (#9) that implements this feature. Could you consider releasing a new version that includes it?

[willhains]

@bohnman I published my fork with #8 and #9 as io.github.willhains:package-info-maven-plugin:1.2.0.