chore(refactor): move config to an internal package

[wolf31o2]

Minor refactoring of the code to move the config.go code into a config package, which we put under internal to indicate that it's not intended to be used outside this code.

• Move config.go to internal/config and change package name to config
• Import config package
• Use config.LoadConfig() to load the initial configuration
• Use config.GetConfig() to get configuration information