add section to add list of attachments for sending email in email workflow

Summary under the email body, there is a button to add email attachments. the attachment can be a link or file from the Directus file library and the link can insert sth like {{$trigger.payload.file_url_from_a_field}}, then when the flow is triggered, it will download those files and attach it to the email Basic Example _No response_ Motivation an email workflow is one of the important tasks for staff to use to create some data and able to send attachments along. another use case is job application form submission, for example, sending the job application email to HR with a resume attached or generally building any form that requires sending some file via email Detailed Design Directus already used NodeMailer to send email and NodeMailer supports sending attachments out of the box so for the backend we can update the email workflow API to accept a list of attachments, read those files' URLs to download them, and attach them to the email. for the web UI under the email b…