**Description**

Files are not part of the templated fields in the `EmailOperator` https://airflow.apache.org/docs/stable/_modules/airflow/operators/email_operator.html

Whle in fact file names should also be templated .

**Use case / motivation**
We want to store files accordingly to the DAGs execution date and further send them to email recipients like so:

```
send_report_email = EmailOperator(
        ....
        files=[
            "/tmp/Report-A-{{ execution_date.strftime('%Y-%m-%d') }}.csv",
            "/tmp/Reportt-B-{{ execution_date.strftime('%Y-%m-%d') }}.csv"
        ]
```

airflow/operators/email.py
send_email(
            self.to,
            self.subject,
            self.html_content,
            files=self.files,
            cc=self.cc,
            bcc=self.bcc,
            mime_subtype=self.mime_subtype,
            mime_charset=self.mime_charset,
        )