New module/section: Effective Pip Count (EPC)

From the wishlist (#2). Suggested as a radar idea, seconded by
@kagsteiner (2 👍).

Effective Pip Count goes beyond the raw count to account for wastage and
crossovers — @kagsteiner notes it's "very tricky but very useful in the
endgame" and would like to be able to train it.

Status: collecting interest. Before this can move forward, it needs the
didactic groundwork — how EPC is taught, which method/source to follow,
and worked examples — plus a decision on whether it's a new Pip Count
section or its own module. To be developed further once that's pinned
down and demand is clear.

Source: https://github.com/hape42/BackgammonGym/discussions/2

Start with wishlist discussion #2 and the issue's stated didactic requirements. Define how Effective Pip Count is taught, choose the method or source, and prepare worked examples; the work is done when there is a decision on a new Pip Count section versus a standalone module and the demand is clear.

Written by the indexing model from the issue text.