chore: fix "git commit" when there is no pdd.json file

The error was:
error: pathspec 'pdd.json' did not match any file(s) known to git

Correction for b7a7af8 commit.

Author: php-coder

.github/workflows/todos-extract-from-code.yml

@@ -165,6 +165,7 @@ jobs:
           NEW_COMMIT_MSG: "chore: processed ${{ env.COMMIT_MSG }}"
         working-directory: generated-todos
         run: |
+          git add pdd.json
           git commit pdd.json todos-in-code.tsv -m "$NEW_COMMIT_MSG"
           git push