ci: build the utf8 version

Author: yutaro-sakamoto

.github/workflows/ci.yml

@@ -6,12 +6,22 @@ on:
     types: [opened, reopened, review_requested, synchronize]
 
 jobs:
-  run-tests:
+  build:
     runs-on: ubuntu-latest
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Build a docker image
         run: docker build -t opensourcecobol/opensourcecobol4j .
+
+  utf8-build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Build a docker image
+        run: docker build -t opensourcecobol/opensourcecobol4j:utf8 . -f utf8.Dockerfile