chore: update vulnerable dependencies and add Maven CI
Bump jackson-databind 2.15.2 -> 2.22.1, logback-classic 1.4.8 -> 1.5.38,
slf4j-api 2.0.7 -> 2.0.17, and netty-all 4.1.94 -> 4.1.136 to clear all
open Dependabot security advisories.
Add a GitHub Actions workflow building on JDK 11, and a .gitignore for
Maven/IDE artifacts.
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