Release Turnstile version 6.0.0-alpha.77.
Release Turnstile version 6.0.0-alpha.77.

 * Upgrade `interrupt` to `11.0.0-alpha.21`.
 * Upgrade `destructible` to `7.0.0-alpha.66`.
 * Upgrade `perhaps` to `0.0.11`.
 * Build with Node.js 16 on GitHub Actions.
 * Build with Node.js 16 on Travis CI.

Closes #271.

bigeasy/turnstile