update pypy3 to point to 3.6 (#164)

.github/workflows/test.yml

@@ -90,3 +90,24 @@ jobs:
 
     - name: Run simple code
       run: python -c 'import math; print(math.factorial(5))'
+
+  setup-pypy:
+    name: Setup PyPy ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-latest, windows-latest, ubuntu-16.04, ubuntu-18.04]
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: setup-python pypy3
+      uses: ./
+      with:
+        python-version: 'pypy3'
+
+    - name: setup-python pypy2
+      uses: ./
+      with:
+        python-version: 'pypy2'