Release Prolific Queue 19.0.1.
Release Prolific Queue 19.0.1.

 * Upgrade `destructible` to `^5.2.0-alpha.2`. Closes #1219.
 * Remove sub-module `.gitignore`. Closes #1218.
 * Revert Prolific Queue test to Proof. Closes #1198.

Closes #1220.

bigeasy/prolific,bigeasy/prolific