Rewrite the README for a released, independently developed project

The README was written as a plan for the fork: why it exists, a five-phase roadmap, prior art and open decisions. 2.98.0.1 is published on Maven Central, the Gradle Plugin Portal, the JetBrains Marketplace and GitHub Releases, so that plan now misleads: it said nothing was published and told readers to keep using upstream. The README becomes a short front page instead: where the artifacts are, links to the documentation on openjavaformat.dev, one output example, the coordinates table for people coming from palantir-java-format, how to build, and the unchanged licence block. The reasons for the project live in the manifesto on the site.

The build section now names what CI runs instead of mise tasks that no longer exist, and a link to an .actrc file that never existed is gone. The badges for Maven Central and the Plugin Portal read the repositories' metadata, because the dedicated shields endpoints return nothing for these coordinates.

Author: abashev