Add: docker installation command in Readme

[1Lucas1apk]

Changes

Placing a subtopic in the installation topic with the docker installation command

Why

Checkmarks

• [x] The modified endpoints have been tested.
• [x] Used the same indentation as the rest of the project.
• [x] Still compatible with LavaLink clients.

Additional information

[UnschooledGamer]

Perhaps adding a NOTE about needing to use docker domain to connect?

Normal system/network ip can be too used.