init github action

.github/workflows/gradle.yml

@@ -0,0 +1,23 @@
+name: CI
+
+on:
+  push:
+    branches: [ action, master ]
+  pull_request:
+    branches: [ action, master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 11
+      uses: actions/setup-java@v1
+      with:
+        java-version: 11
+    - uses: eskatos/gradle-command-action@v1
+      with:
+        gradle-version: 6.8
+        arguments: test

build.gradle.kts

@@ -30,11 +30,11 @@ tasks.withType<KotlinCompile> {
 
 val compileKotlin: KotlinCompile by tasks
 compileKotlin.kotlinOptions {
-    jvmTarget = "1.8"
+    jvmTarget = "11"
 }
 val compileTestKotlin: KotlinCompile by tasks
 compileTestKotlin.kotlinOptions {
-    jvmTarget = "1.8"
+    jvmTarget = "11"
 }
 
 tasks.test {