Clarify that the official rules are the English ones.
Reword the describtion of the linked pages.

Remove unused css and introduce line breaks for better readability.

The previous make/shell based approach results in only a single
placeholder id 'placeholder-0' because we invoke generate_card.py
for each card which will initialize the placeholder id count each time
with 0.
Now we generate the whole car listing in python which greatly reduces
the number of program invocations and allows the placeholder id
to be incremented for each listed card.