[pyos][docs] practical examples should be self-contained

[giovana-morais]

part of pyOpenSci/software-submission#267 (comment)

in the practical examples section of the documentation, it would be very useful to have simple files (1 or 2 entries each) to showcase what the library is actually doing.

for example, it is unclear what it means to "enhance" a bib entry. i'm assuming that it is completing the missing fields, but i cannot ensure that this is the case because it is the first time "enhancement" appears.