fix: Add JRE 18 to publish-example-site job

This should fix the `UnsupportedClassVersionError` which occurred when
generating the example site in the release workflow.

.github/workflows/release.yml

@@ -142,6 +142,10 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v3
+      - uses: actions/setup-java@v3
+        with:
+          distribution: temurin
+          java-version: 18
 
       - name: Download binaries
         uses: actions/download-artifact@v3
@@ -159,7 +163,7 @@ jobs:
           build/install/structurizr-site-generatr/bin/structurizr-site-generatr generate-site
           --git-url https://github.com/avisi-cloud/structurizr-site-generatr.git
           --workspace-file docs/example/workspace.dsl
-          --branches main 
+          --branches main
           --default-branch main
           --version ${{ github.ref_name }}