Adding a global before_script/after_script to the ymal file

Basically, in the scripts section, you will add a lot of commands that you will execute in each pipeline so why don't we have a global command like image which will be used as the default commands that will be executed before executing any other command.

And it can be overwritten with in any section if they want, by just define a new before_script section inside the section itself then it will ignore the global one.

This is a feature that found on Gitlab-ci and I do find it better to clean up the file a bit.

The same will be for after_script as it will also make it easy to clean up after executing the code.