Added github action to run pytest

Author: nickanderson

.github/workflows/ci.yml

@@ -2,7 +2,7 @@ name: Continuous Integration
 
 on:
   pull_request:
-    types: [opened, reopened]
+    types: [opened, reopened, synchronize]
 
 jobs:
   unit_tests:
@@ -22,3 +22,7 @@ jobs:
       run: cfbs validate
     - name: Check the formatting
       run: cfbs --check pretty ./cfbs.json
+    - name: Install pytest
+      run: pip install pytest
+    - name: Run promise type tests
+      run: python3 -m pytest promise-types/ -v