Migrate Easel with open-source-library-migration guide

[theJawnnybot]

Summary

Applied open-source-library-migration.md to Easel.

Build/toolchain

• Java 17
• Gradle 9.3.1
• Android Gradle Plugin 9.1.0
• Converted build scripts from Groovy to Kotlin DSL (.gradle.kts)
• Updated dependencies to latest stable

Publishing

• Migrated to Maven Central via com.vanniktech.maven.publish
• Configured publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
• Enabled release signing in workflow
• Added/updated POM metadata in gradle.properties
• Patch bump: VERSION_NAME=3.1.1

CI/CD

• Modernized CI workflow (checkout@v4, setup-java@v4, wrapper validation)
• Added tag-based publish workflow using:
  • MAVEN_CENTRAL_USERNAME
  • MAVEN_CENTRAL_PASSWORD
  • SIGNING_PRIVATE_KEY
  • SIGNING_PASSWORD
• Publish uses tag version argument:
  • -PVERSION_NAME="${GITHUB_REF_NAME}"

Docs/cleanup

• Replaced JitPack/Travis README badges with GitHub Actions + Maven Central
• Updated dependency snippet to Maven Central coordinates

Validation

• GRADLE_USER_HOME=/tmp/gradle-easel ./gradlew build ✅