[3.13] gh-136162: Document `encodings` package functions (GH-136164) (#136453)

gh-136162: Document `encodings` package functions (GH-136164)

Closes GH-136162.
(cherry picked from commit ffd7f2f231f5543e6863c6c85e86f72233229771)

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>