Configure project to explicitly use JDK 11 for IntelliJ recognition

[Copilot]

This PR configures the Gradle build to explicitly specify JDK 11 requirements, ensuring IntelliJ IDEA and other IDEs properly recognize and use the correct Java version when importing the project.

Changes Made

build.gradle

• Added Java toolchain configuration using Gradle's modern toolchain API:

  java {
      toolchain {
          languageVersion = JavaLanguageVersion.of(11)
      }
  }

• Configured Kotlin compilation to target JVM 11:

  compileKotlin {
      kotlinOptions {
          jvmTarget = "11"
      }
  }
  compileTestKotlin {
      kotlinOptions {
          jvmTarget = "11"
      }
  }

gradle.properties (new file)

• Added explicit Java version documentation:

  # Java version configuration
  # Explicitly set Java version requirement
  java.version=11

README.adoc

• Updated development section to clearly document Java 11 requirement
• Added Requirements subsection for better developer onboarding

Benefits

1. IntelliJ IDEA will automatically detect and configure JDK 11 when importing via Gradle
2. Gradle toolchain will automatically download JDK 11 if not available locally
3. Consistent builds across different development environments
4. Clear documentation for contributors about Java version requirements

The project has been using Java 11 since version 1.8.0 (as noted in CHANGELOG.md), but the build configuration didn't explicitly enforce this requirement. These changes make the Java 11 dependency explicit and automatic.

Fixes #83.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• cache-redirector.jetbrains.com
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.lang.invoke=ALL-UNNAMED --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.prefs/java.util.prefs=ALL-UNNAMED --add-opens java.prefs/java.util.prefs=ALL-UNNAMED --add-opens java.base/java.nio.charset=ALL-UNNAMED --add-opens java.base/java.net=ALL-UNNAMED --add-opens java.base/java.util.concurrent.atomic=ALL-UNNAMED -XX:MaxMetaspaceSize=256m -XX:+HeapDumpOnOutOfMemoryError -Xms256m -Xmx512m -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp /home/REDACTED/.gradle/wrapper/dists/gradle-7.2-bin/2dnblmf4td7x66yl1d74lt32g/gradle-7.2/lib/gradle-launcher-7.2.jar org.gradle.launcher.daemon.bootstrap.GradleDaemon 7.2 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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[ehmkah]

Please add an entry to changelog what you changed

[Copilot]

Please add an entry to changelog what you changed

Added changelog entry for the Gradle build configuration changes in commit c2807e2.