adding github actions for testing

.github/workflows/testing.yml

@@ -0,0 +1,30 @@
+name: Testing
+on: [push]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.5, 3.6, 3.7, 3.8]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r tests-requirements.txt
+        pip install -r requirements.txt
+        npm install -g remark-cli remark-validate-links
+        npm install -g markdown-link-check
+    - name: Run tests
+      run: |
+        ./tests.sh
+      env:
+        DOTDROP_FORCE_NODEBUG: yes
+        DOTDROP_NOBANNER: yes
+    - name: Coveralls
+      run: |
+        coveralls