Allow execution of additional setup steps / script

[ssbarnea]

Quite often in order to prepare WSL on a machine we need more than installing additional-packages and allowing addition of an extra step, would greatly simplify maintenance of GHA that use WSL.

I am aware that we can run extra steps after, but these would need to be verbose as we would have to duplicate the same conditions for setting WSL (wsl being only one matrix testing scenario).

Maybe we need two commands:

• pre-install-script - to run before additional-packages are installed, very useful for those that need to enable additional deb repos
• post-install-script - to run after additional-packages are installed

WDYT?

[Vampire]

I'm not sure how that makes things easier that warrants the added feature.
What is the problem with having just another run-step that does the needed things and if they need to be done before installing additional packages just doing the install call as part of that separate run step, or just calling this action again with the additional packages option with your run step in-between.

Can you maybe show how it looks now and how it would potentially look like with this feature added that improves your maintenance experience?