Improve documentation on how to deploy for a private network

[luislhl]

We have poor documentation and this makes it hard for people to deploy the Explorer and Explorer-service on their own environments.

We need a guide on how to do this.

The guide should include how to run them locally for development and how to do a production-ready deployment.

For running locally, we already have a docker-compose.yml, but it should be reviewed and improved as needed.
The .env.example file should also be updated and documented (see #261)

For running in production, we should have guides on how to run the Serverless deploy, how people could replicate our CI/CD pipeline (maybe by forking the repo and using Github Actions?), and how to deploy the necessary dependencies (Elasticsearch, WalletService database, Redis, Daemon).

Feature Flags should be implemented in order to disable certain features that not everyone may need, which could remove the need for some of the dependencies. For instance, to avoid having to deploy an Elasticsearch, we should allow disabling the charts in the Explorer Statistics page.

Be aware that the Explorer already has support for some feature flags. This can be seen in (internal link): https://github.com/HathorNetwork/ops-tools/blob/master/docs/sops/hathor-explorer.md#feature-flags