🚥 Test cross-platform support via Workflows (#6)

.github/workflows/platforms.yml

@@ -0,0 +1,40 @@
+name: Test Cross Platform Support
+
+on: [push]
+
+jobs:
+  linux:
+    runs-on: ubuntu-latest
+    name: Extract Example File on Ubuntu
+    steps:
+      - uses: actions/checkout@v2
+      - run: docker build -t example:${{ github.sha }} ./.github/tests
+      - uses: ./
+        id: extract
+        with:
+          image: example:${{ github.sha }}
+          path: /files/001.txt
+      - run: test -e ${{ steps.extract.outputs.destination }}/001.txt || exit 1
+  macos:
+    runs-on: macos-latest
+    name: Extract Example File on macOS
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Docker Machine
+        run: |
+          brew install docker docker-machine
+          docker-machine create --driver virtualbox default
+          eval $(docker-machine env default)
+          env | grep DOCKER >> $GITHUB_ENV
+      - run: docker build -t example:${{ github.sha }} ./.github/tests
+      - uses: ./
+        id: extract
+        with:
+          image: example:${{ github.sha }}
+          path: /files/001.txt
+      - run: test -e ${{ steps.extract.outputs.destination }}/001.txt || exit 1
+  windows:
+    runs-on: windows-latest
+    name: Extract Example File on Windows
+    steps:
+      - run: echo "Docker is not supported in GitHub's hosted Windows runners"