Log Message:
devel/hs-optparse-applicative: Add a mk fragment application.mk

optparse-applicative has a really nice feature that enables any tools
parsing command-line arguments with the library to automatically generate
bash, fish, and zsh completion scripts via hidden options, by hidden it
means they aren't shown in the "--help" message.

Packages that install executables using optparse-applicative can now
include this file to automatically generate and install such scripts.