Update CI to use newer maven builds, prep for java 21

Author: niloc132

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly

.github/workflows/build.yml

@@ -7,6 +7,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     strategy:
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
     steps:
@@ -34,15 +35,20 @@ jobs:
     runs-on: ubuntu-latest
 
     strategy:
+      fail-fast: false
       matrix:
-        mvn: ['3.8.6', '3.6.3', '3.5.4', '3.3.9', '3.2.5']
+        mvn: ['3.9.5', '3.8.8', '3.6.3', '3.5.4', '3.3.9', '3.2.5']
         java: ['11']
 #        include: # Confirm that old java works in the oldest maven, and that newest maven supports 8-current
 #            #TODO j2clmavenplugin#159 - re-enable this when the integration tests run cleanly in Java 17+
-#          - mvn: '3.8.6'
+#          - mvn: '3.8.8'
 #            java: '17'
-#          - mvn: '3.8.6'
-#            java: '18'
+#          - mvn: '3.8.8'
+#            java: '21'
+#          - mvn: '3.9.5'
+#            java: '17'
+#          - mvn: '3.9.5'
+#            java: '21'
     steps:
       - name: Checkout
         uses: actions/checkout@v2