Add OpenMSX.app v0.11.0

openMSX is an emulator for the MSX home computer system.
Seeing as `url` doesn’t point to a specific version, this cask should use `version :latest` and `sha256 :no_check`. [See an example](https://github.com/caskroom/homebrew-cask/blob/master/Casks/acorn.rb).