make sure punkt_tab is available

Author: lwgray

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -r tests/requirements.txt
-        python -m nltk.downloader popular punkt
+        python -m nltk.downloader popular punkt punkt_tab
 
     - name: Run Unit Tests
       run: |