Make list.txt and example code more intuitive

[vvye]

Over the past few years, many people have mistaken the effects of the example code for a bug, because they didn't know that it was there, and that the entries in list.txt existed. It's become clear that the presence of the example code is confusing, or wasn't conveyed well.

I have attempted to fix this by:

• changing list.txt to be tidier and easier to read
• including more eye-catching info on how to use the lists in list.txt
• giving each list exactly one example entry, with its own code file that does nothing (the files have a comment in them explaining that they can be removed, but, crucially, nothing weird happens if they aren't removed).

[vvye]

I should probably mention this fixes #21.

[VitorVilela7]

Thank you for the pull request @vvye, it's always important to make documentation clarifying as possible for the end-user experience.