This issue is related to #555

#466 introduced a configuration manager. Currently, it only reads from environment variables. For configuration files to be read, then it is necessary to define a few things first:

1. Where the configuration file would be located?
2. Do we want several formats to be supported or only one?
3. Which format or formats do we want to support?

Here are some formats for consideration:

1. JSON
2. YAML
3. TOML
4. Python (like Django does for its settings file)
5. INI

Please leave your thoughts about this in the comments below.