Bumps base Docker image to Java 21, modifies ENTRYPOINT to be absolute.

Dockerfile

@@ -1,10 +1,11 @@
-FROM eclipse-temurin:17.0.8.1_1-jre-jammy
+FROM eclipse-temurin:21.0.1_12-jre-jammy
 
-WORKDIR /usr/local/structurizr-cli/
-ENV PATH /usr/local/structurizr-cli/:$PATH
-COPY build/distributions/structurizr-cli-*.zip ./
-RUN apt-get update && apt-get install -y unzip  && apt install -y graphviz && rm -rf /var/lib/apt/lists/*
-RUN unzip /usr/local/structurizr-cli/structurizr-cli-*.zip && chmod +x structurizr.sh
-WORKDIR /usr/local/structurizr/
+RUN apt-get update && apt-get install -y unzip && apt install -y graphviz && rm -rf /var/lib/apt/lists/*
 
-ENTRYPOINT ["structurizr.sh"]
+COPY build/distributions/structurizr-cli-*.zip /tmp
+
+RUN unzip /tmp/structurizr-cli-*.zip -d /usr/local/structurizr-cli && chmod +x /usr/local/structurizr-cli/structurizr.sh
+
+WORKDIR /usr/local/structurizr
+
+ENTRYPOINT ["/usr/local/structurizr-cli/structurizr.sh"]