Build Status Badge in git README

In order to aid developers and DevOps engineers who are working in a git-driven ecosystem, it would be helpful to see the status builds in the README. This is a standard for many open source projects. I think one could debate whether we should have a multi-line build badge visual in the README because people need to know about the builds for various versions and platforms in the case of Lucene/Solr because it is such a large and widely used project, in a variety of environments. The badges not only celebrate that fact, they support its persistence in the future with new developers who look for such information instictively.

I would recommend the active build pipelines (currently 8.x and 9.x) for each platform, Linux, Windows, MacOSX, and Solaris.