added files

.devcontainer/Dockerfile

.devcontainer/devcontainer.json

.gitignore

build.gradle

gradle/wrapper/gradle-wrapper.jar

gradle/wrapper/gradle-wrapper.properties

gradlew

gradlew.bat

settings.gradle

src/main/java/dotsandboxes/DotsAndBoxesGrid.java

src/main/java/dotsandboxes/DotsAndBoxesUI.java

src/main/java/dotsandboxes/Main.java

src/test/java/dotsandboxes/DotsAndBoxesGridTest.java

src/test/resources/log4j2.xml