Migrate ModalBottomSheetDialogFragment with open-source-library-migration guide

[theJawnnybot]

Summary

Applied the migration checklist in open-source-library-migration.md.

Build/toolchain

• Java 17
• Gradle 9.3.1
• AGP 9.1.0
• Converted all build scripts from Groovy to Kotlin DSL (.gradle.kts)
• Updated Android dependencies to current stable versions

Publishing

• Switched to Maven Central using com.vanniktech.maven.publish
• Configured publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
• Enabled signing for release workflow
• Added/updated gradle.properties metadata (and patch bump to VERSION_NAME=1.3.1)

CI/CD

• Modernized ci.yml (checkout v4, setup-java v4, wrapper validation)
• Added tag-based publish workflow using:
  • MAVEN_CENTRAL_USERNAME
  • MAVEN_CENTRAL_PASSWORD
  • SIGNING_PRIVATE_KEY
  • SIGNING_PASSWORD
• Uses tag version via -PVERSION_NAME="${GITHUB_REF_NAME}" (no file mutation in CI)

Docs/cleanup

• Removed JitPack config (.jitpack.yml) and JitPack README snippets
• Added Maven Central badge + dependency snippet

Validation

• ./gradlew build ✅