systeminformation gets incorrect memory information due to BusyBox's
"free" issue.(#3409)
A workaround for avoiding it was made.
But it never works because the runner container has no effect.
It should be deleted.
* Revert "Update Dockerfile (#4090)"
This reverts commit 6758b0f133.
* Docker: Add ffmpeg package for the runner container
Misskey 10.81.0 added thumbnail generation support.
However it did not work with Docker bacause ffmpeg has not been
installed in the runner container.
* Modify Dockerfile and docker-compose.yml
* Fix MongoDB connection error
* Use alpine-3.8 instead of alpine-edge as base image
* Modify install packages
* Modify Mongodb image tag name
* Update Docker documents
* Add 'Download misskey' paragraph
* Make redis optional for Docker
* Dockerize Misskey
* Add a new line at EOF
* Add support Elasticsearch
* /
* Add setup document for docker
* Add english document
* Edit docs
* docker -> Docker
* Arrange format
* Update docker.en.md
* Modify title
