Ability to add multiple pre or post scripts

Kindly add the ability to add multiple pre or post install/uninstall scripts and the ability to manage their execution priority.

This would simplify the onboarding for new customers when trying to migrate their existing packages to PMPC; it would negate the need to refactor their existing scripts into a single script, especially if there are multiple scripts in different languages.

In summary:

• Add support to upload multiple pre or post scripts

• Allow the same for both install and uninstall

• Allow mixing of all currently supported scripting languages

• Define successful exit codes for each script

• Allow ability to toggle "continue on error" per script