GitHub action execute-modified-python-file.yml will not run when a new file is created and added to repo

**About Bug or problem**
The GitHub action to execute python file will not run when a file is created rather than modified.
This is because the action is designed only to check files that were **modified** and so will ignore files that are new to the repo.

**Steps to reproduce**
Create a brand new python file and add to the repo. The GitHub action will not see any files as being modified and will print:
```
Run echo "job: running script to execute modified file:"
job: running script to execute modified file:
run-sh: Inside run-modified-python.sh
run-sh: Content of files_modified.json: []
run-sh: After parsing, file to execute:
run-sh: File modified is not a python file! Will not execute
job: Done
```

**Potential fix**
Modify action `execute-modified-python-file.yml` to detect when new files are added to the repo and execute them.