Document how to run celestia-app via Docker

[rootulp]

Context

This repo publishes Docker images to https://github.com/celestiaorg/celestia-app/pkgs/container/celestia-app/versions

Problem

The current README has sections under the Install section for Source and Prebuilt binary but it doesn't have a section for Docker.

Proposal

Readers may be unaware that they can run celestia-app via Docker. We should add a sub-heading to the Install section that describes how users can use the Docker image. Things we may want to include in this section:

• Prerequisites (i.e. must have Docker version X installed, must have Y resources allocated to Docker).
• Copy + paste-able commands to fetch the latest tagged release
• A Docker compose file

[MukulKolpe]

Hey @rootulp, can I work on this issue?

[kaksv]

Docker is really amazing