pbp shooter column silently removed in 2.2.0 — deprecate or document #88

Context

On the 2.2.0 branch, the play-by-play `shooter` column from 2.1.x was replaced by `player_name` (broader semantics: the primary actor on any attributed play, sourced from ESPN's structured JSON with a text-parse fallback). Unlike `game_day`/`game_time` and `half`/`quarter`, which got deprecation shims, a CHANGELOG entry, and coverage in `DEPRECATED_COLUMNS`, `shooter` just disappeared — existing consumer code selecting it breaks with a KeyError and there's no changelog trace.

Decide before release

Either:

1. Deprecate: re-emit `shooter` (populated only on shooting plays, as before), add it to `DEPRECATED_COLUMNS` with `player_name` as its replacement and 3.0 removal, or
2. Document the removal: add a "Removed" entry to CHANGELOG.md's 2.2.0 section.

Also

The README pbp example table still shows the old schema: a `shooter` column and old lowercase `play_type` values (`jumper`, `jump ball`) instead of the new JSON types (`JumpShot`, `Jump Ball`). Regenerate the example table either way.