Feature Request: Add support for file uploads in requests

[lvisb]

I would like to suggest adding a new feature that allows file uploads in requests. Currently, the system does not support file uploads, which limits some use cases.

I would suggest using a key character to identify uploads, such as @ followed by the file path in the system. For example: @/home/user/file.png.

[Mr-Destructive]

Have added a simple approach for this on #231
The @ part is quite a standard approach for file uploads taken from the curl ecosystem.
Let me know your thoughts