Update GHA (#5)

.github/workflows/dd-javac-plugin-tests.yaml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - '*'
+  workflow_dispatch:
 
 jobs:
   run-tests-jdk-8:
@@ -13,9 +14,12 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
-          java-version: "17"
+          java-version: |
+            8
+            9
+            17
           distribution: "adopt"
       - name: run-unit-tests
         run: ./gradlew test -PtestJdkVersion=8
@@ -27,9 +31,13 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
-          java-version: "17"
+          java-version: |
+            8
+            9
+            11
+            17
           distribution: "adopt"
       - name: run-unit-tests
         run: ./gradlew test -PtestJdkVersion=11
@@ -41,23 +49,30 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
-          java-version: "17"
+          java-version: |
+            8
+            9
+            17
           distribution: "adopt"
       - name: run-unit-tests
         run: ./gradlew test -PtestJdkVersion=17
 
-  run-tests-jdk-20:
-    name: run-unit-tests-jdk-20
+  run-tests-jdk-21:
+    name: run-unit-tests-jdk-21
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
-          java-version: "17"
+          java-version: |
+            8
+            9
+            17
+            21
           distribution: "adopt"
       - name: run-unit-tests
-        run: ./gradlew test -PtestJdkVersion=20
+        run: ./gradlew test -PtestJdkVersion=21