add action to build java jar

.github/workflows/ci-java.yml

@@ -0,0 +1,36 @@
+on: 
+    pull_request:
+      paths:
+        - .github/actions/extism/**
+        - .github/workflows/ci-java.yml
+        - manifest/**
+        - runtime/**
+        - libextism/**
+        - java/**
+    workflow_dispatch:
+
+  name: Java CI
+
+  jobs:
+    java:
+      name: Java
+      runs-on: ${{ matrix.os }}
+      strategy:
+        matrix:
+          os: [ubuntu-latest]
+          version: [11, 17]
+          rust:
+            - stable
+      steps:
+        - name: Checkout sources
+          uses: actions/checkout@v3
+        - uses: ./.github/actions/extism
+        - name: Set up Java
+          uses: actions/setup-java@v3
+          with:
+            distribution: 'temurin'
+            java-version: '${{ matrix.version }}'
+        - name: Test Java
+          run: |
+            cd java
+            mvn --batch-mode -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=warn verify