Add a ZIP AttachmentType for the Attach File keyword #442

I'm submitting a ...

• [X ] feature request

What is the current behavior?

I would like to use the Robot Framework "AllureLibrary.Attach File" keyword with a .zip file.
Currently, ZIP is not available as AttachmentType. So the downloaded file is a ".attach" file that I have to rename as a .zip file.

What is the expected behavior?

I would like to be able to set attachment_type to ZIP for the "AllureLibrary.Attach File" keyword, so that I can directly download the .zip file.

• Allure version: 2.12.1
• Test framework: robotframework@3.0.2
• Allure adaptor: allure-robotframework@2.8.6