Add documentation & explanations

[codergeek42]

Minus a tiny mention in src/lib/nextWordGuesserStrategy.ts, the current documentation is...basically nonexistent other than the code being its own source of truth (which is not exactly obvious in many spots).

Acceptance Criteria:

1. Each class and method is TSDoc documented;
2. the README is expanded to explain the solver logic and each scoring method used;
3. Antora docs are generated as applicable; and
4. Clean up the more intricate/unreadable portions of solver code (use more named intermediary variables & comments, etc.).