Allow/Support centralized configuration

[nbeDPDHL]

Since we want to use this extension in many different repositories and we almost always want the same configuration it would be nice if there was a way to configure the extension centrally (for example in another repo). A good example would be the shareable config presets like renovate uses them: https://docs.renovatebot.com/config-presets/

[qoomon]

Nice idea, however I don't have the time currently. Any PR is welcome.
Starting point would be here

maven-git-versioning-extension/src/main/java/me/qoomon/maven/gitversioning/GitVersioningModelProcessor.java

Line 1032 in 86acfc9

private static Configuration readConfig(File configFile) throws IOException {

[nbeDPDHL]

Alright, thanks. I will see if I can find the time :)