Allow custom scripts in the Mintfile

[dcarmo-tribalscale]

Feature Request:

It would be nice to be able to add run scripts to the Mintfile much like how npm allows custom script definitions in the packages.json. At the moment I supplement with a makefile, but it would be nice to remove another tool and just use Mint for it.

e.g.

Mintfile

# Help to generate the xcodeproj file
# https://github.com/yonaskolb/XcodeGen
yonaskolb/XcodeGen@2.32.0

setup:
  mint bootstrap
  mint run xcodegen

xcodegen:
  mint run xcodegen@2.32.0 --spec Shared/project.yml	
  mint run xcodegen@2.32.0 --spec Database/project.yml
  mint run xcodegen@2.32.0 --spec App/project.yml

run using

mint run setup