Use yarn (#5154)

* Revert "✌️"

This reverts commit b5b437b878.

* 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

docs/docker.ja.md

@@ -68,7 +68,7 @@ cp docker_example.env docker.env
 *5.* データベースを初期化
 ----------------------------------------------------------------
 ``` shell
-docker-compose run --rm web npm run init
+docker-compose run --rm web yarn run init
 ```
 
 *6.* 以上です！