Cleanup README (#392)

The README has gotten quite bloated and needed to be cleaned up.
Contributing information is moved to `CONTRIBUTING.md`, usage info is in
`USAGE.md`, and the `README.md` is now much easier to read and follow.

Author: WesJD

CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing to AnvilGUI
+
+The project uses the Maven. Run `mvn clean install` using Java 21 to build the project.
+
+## Formatting
+
+The project uses the [Spotless Maven Plugin](https://github.com/diffplug/spotless/tree/main/plugin-maven) to
+enforce style guidelines. You will not be able to build the project if your code does not meet the guidelines.
+To fix all code formatting issues, run `mvn spotless:apply`.
+
+## Deployment
+
+The code is built and deployed to `mvn.wesjd.net` via GH actions whenever a push to `master` occurs.