add code coverage driver to workflow

Author: patinthehat

.github/workflows/run-tests.yml

@@ -23,7 +23,7 @@ jobs:
         with:
           php-version: ${{ matrix.php }}
           extensions: dom, curl, libxml, mbstring, zip, pcntl, pdo, sqlite, pdo_sqlite, bcmath, soap, intl, gd, exif, iconv, imagick, fileinfo
-          coverage: none
+          coverage: pcov
 
       - name: Setup problem matchers
         run: |