[Installation Support Idea] Make this guide a Docker Compose File

This issue has been migrated from [#13895](https://github.com/matrix-org/synapse/issues/13895).

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**Description:**

This guide is a basic setup that most people starting their own server would be aiming to achieve. Make a docker compose file for this setup. Link it in this guide. A docker compose file would answer most the questions people have about a setup.

https://matrix.org/blog/2020/04/06/running-your-own-secure-communication-service-with-matrix-and-jitsi