update docs

Author: ks6088ts

.vscode/extensions.json

@@ -0,0 +1,6 @@
+{
+    "recommendations": [
+        "Oracle.oracle-java",
+        "vscjava.vscode-java-pack"
+    ]
+}

README.md

@@ -1,2 +1,48 @@
+[![test](https://github.com/ks6088ts-labs/sandbox-java/actions/workflows/test.yaml/badge.svg?branch=main)](https://github.com/ks6088ts-labs/sandbox-java/actions/workflows/test.yaml?query=branch%3Amain)
+[![docker](https://github.com/ks6088ts-labs/sandbox-java/actions/workflows/docker.yaml/badge.svg?branch=main)](https://github.com/ks6088ts-labs/sandbox-java/actions/workflows/docker.yaml?query=branch%3Amain)
+[![ghcr-release](https://github.com/ks6088ts-labs/sandbox-java/actions/workflows/ghcr-release.yaml/badge.svg)](https://github.com/ks6088ts-labs/sandbox-java/actions/workflows/ghcr-release.yaml)
+
 # sandbox-java
+
 A sandbox for Java
+
+## Prerequisites
+
+- [JDK 21+](https://www.oracle.com/java/technologies/downloads/)
+- [GNU Make](https://www.gnu.org/software/make/)
+
+## Development instructions
+
+### Local development
+
+Use Makefile to run the project locally.
+
+```shell
+# help
+make
+
+# install dependencies for development
+make install-deps-dev
+
+# run tests
+make test
+
+# build applications
+make build
+
+# run CI tests
+make ci-test
+```
+
+### Docker development
+
+```shell
+# build docker image
+make docker-build
+
+# run docker container
+make docker-run
+
+# run CI tests in docker container
+make ci-test-docker
+```

docs/README.md

@@ -0,0 +1,7 @@
+# References
+
+- [Java Platform Extension for Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=Oracle.oracle-java)
+- [Extension Pack for Java](https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-pack)
+- [Gradle > Installation](https://gradle.org/install/)
+- [Gradle > Tutorial](https://docs.gradle.org/current/userguide/part1_gradle_init.html)
+- [Could not find or load main class org.gradle.wrapper.GradleWrapperMain](https://stackoverflow.com/a/29806323/4457856)