Use yarn (#5154)

* Revert "✌️"

This reverts commit b5b437b8.

* Welcome back, yarn.lock

[lockfiles for all](https://yarnpkg.com/blog/2016/11/24/lockfiles-for-all/)

* Use alpine package registry instead of npm's

* Avoid npx

* Remove `"`

* Follow review

refs: https://github.com/syuilo/misskey/pull/5154#discussion_r303227256

* Update lockfile

* Use yarn instead of npm run

refs: https://github.com/syuilo/misskey/pull/5154#discussion_r303227285

* Back to npm

* Follow review

refs: https://github.com/syuilo/misskey/pull/5154#discussion_r303292279