A couple of optimizations are done in this PR. One, we now will check config ahead of time to see if a module is disabled before running any module code. Also, we won't try to discover a git repository unless the module requests access to it.
• Add support for the disabled configuration option
This will allow you to selectively disable modules that you don't want or need. 😄
• Overwrite starship configuration file path with STARSHIP_CONFIG environment variable
• Write tests for the two configuration options that are available
- Create `Config` struct that is added to `Context` when initialized
- Read `~/.confg/starship.toml` during initialization (can be updated later to also look at `$XDG_CONFIG_HOME`)
- `Context` now has a method for creating modules. This allows us to provide modules with a reference to the configuration specific to that module
