fix: Set xp() function as a global function

What is this merge request?

This is a proposal to fix issue #20 .

Also, the code in main did not work out of the box, seemingly because the structure of the web pages being scraped changed since the code in main was written. We amended the code (in 763415e7) in scrap/orange.py and scrap/sosh.py to reflect this.

What approach is used?

We created a new file (scrap/helper.py) which contains a xp function (as well as some constants) used in multiple files. This avoids having duplicate code.