feat: add OCI labels and README push for Docker Hub

Add OCI standard labels to Dockerfile.ci and push README.md to
Docker Hub image page via docker-pushrm in CI workflow.

Dockerfile.ci

@@ -2,6 +2,18 @@ FROM amazoncorretto:21-alpine
 WORKDIR /app
 
 ARG JAR_FILE
+ARG IMAGE_VERSION=dev
+ARG IMAGE_VENDOR=OnixByte
+ARG BUILD_DATE
+
 COPY ${JAR_FILE} app.jar
 
+LABEL org.opencontainers.image.title="delta-force-guide-server" \
+      org.opencontainers.image.description="REST API backend for managing Delta Force game firearm builds and modifications" \
+      org.opencontainers.image.version="${IMAGE_VERSION}" \
+      org.opencontainers.image.vendor="${IMAGE_VENDOR}" \
+      org.opencontainers.image.source="https://git.onixbyte.com/onixbyte/delta-force-guide-server" \
+      org.opencontainers.image.licenses="MIT" \
+      org.opencontainers.image.created="${BUILD_DATE}"
+
 ENTRYPOINT ["java", "-jar", "app.jar"]