Shift to bun

[ENvironmentSet]

While solving #4, I found using Bun is the most simple solution. It has built-in jest-compatible test runner for both javascript and typescript. There is no need to struggle to learn unfamiliar api and no need to setup cumbersome addons for test runners to have compatibility with typescript.

I want to move further, however, I want not only to adapt Bun's test runner but also to adapt whole Bun utilities. Bun is more performant and typescript-friendly than Node.js and npm. With Bun, we can keep things simple and even make things simpler.

Few weeks ago, alpha version of Bun was finally released. It seems to be stabilized. I think now is the best time to adapt Bun in this project. Any opinions?