update mix with a generated script

@erikareads

This allows for completing other tasks that have been installed rather than a static list

[x] This compdef is not already available in zsh.
[x] This compdef is not already available in their original project.
[x] I am the original author, or I have authorization to submit this work. It is apache, so I put the license in the file.
[x] This is a finished work.
[x] It has a header containing authors, status and origin of the script.
[x] It has a license header or I accept that it will be licensed under the terms of the Zsh license.

zsh-users / zsh-completions