Native window decorations: initial implementation in C++ using JNI

.github/workflows/natives.yml

@@ -0,0 +1,56 @@
+# https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
+
+name: Native Libraries
+
+on:
+    push:
+        branches:
+            - '*'
+        tags:
+            - '[0-9]*'
+        paths:
+            - '**.cpp'
+            - '**.h'
+    pull_request:
+        branches:
+            - '*'
+        paths:
+            - '**.cpp'
+            - '**.h'
+
+jobs:
+    Windows:
+        runs-on: windows-latest
+
+        steps:
+            - uses: actions/checkout@v2
+
+            - uses: gradle/wrapper-validation-action@v1
+
+            - name: Setup Java 1.8
+              uses: actions/setup-java@v1
+              with:
+                  java-version: 1.8
+
+            - name: Cache Gradle wrapper
+              uses: actions/cache@v1
+              with:
+                  path: ~/.gradle/wrapper
+                  key: ${{ runner.os }}-gradle-wrapper-${{ hashFiles('gradle/wrapper/gradle-wrapper.properties') }}
+
+            - name: Cache Gradle cache
+              uses: actions/cache@v2
+              with:
+                  path: ~/.gradle/caches
+                  key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle.kts') }}
+                  restore-keys: ${{ runner.os }}-gradle
+
+            - name: Build with Gradle
+              run: ./gradlew :flatlaf-natives-windows:build
+
+            - name: Upload artifacts
+              uses: actions/upload-artifact@v2
+              with:
+                  name: FlatLaf-natives-windows-build-artifacts
+                  path: |
+                      flatlaf-natives/flatlaf-natives-windows/build