just for `bytes32`. ``` push(bytes32 x); pop(); top(); top(uint i); clear(); size(); ``` <!-- Emoji Table: --> <!-- readme/docs 📝 --> <!-- new feature ✨ --> <!-- refactor/cleanup ♻️ --> <!-- nit 🥢 --> <!-- security fix 🔒 --> <!-- optimization ⚡️ --> <!-- configuration 👷♂️ --> <!-- events 🔊 --> <!-- bug fix 🐞 -->