FileActions : allow to register multiply mime types at once

[bigcat88]

Describe why it is important and where it will be useful

While writing an example of an archiver in Go, I encountered a problem that it would be convenient to specify several mimetypes for one endpoints at once.

Could we do this little breaking change before we go too far?

Describe your proposed solution

"fileActionMenuParams": Payload{
    "name":           "unpack",
    "display_name":   "Unpack",
    "mime":           []string{"application/gzip", "application/7z"},
    "permissions":    31,
    "action_handler": "/unpack",
},

Change "mime" from string to list.

Describe alternatives you've considered, if relevant

None

Additional context

No response