Implement config file support

[bmish]

Fixes #95.

README documentation located here.

TODO:

• Add tests
• Use a JSON schema (ajv) to validate config file
• Fix boolean options
• Throw error when duplicate --config-emoji

[MichaelDeBoey]

You can use Record instead. You will get type errors if you the values aren't in sync with OPTION_TYPE

Suggested change

	// TODO: use TypeScript 4.9 satisfies keyword ([key in OPTION_TYPE]...) to ensure all options are included without losing type information.
	export const OPTION_DEFAULTS = {
	export const OPTION_DEFAULTS: Record<OPTION_TYPE, string> = {

[bmish]

Thanks for the suggestion, just tried it and it looks like it's equivalent to the type I was originally trying to use { [key in OPTION_TYPE]: string | string[] | boolean | undefined } and has the same problem. While it does correctly ensure all options are included in the object, it loses type information since accessing a single option from the object now could have any of those possible types instead of what should be a known type. The new satisfies feature in TypeScript 4.9 looks like it will solve this.

[MichaelDeBoey]

Can you elaborate on why you need the exact type for each of them?
It doesn't seem like it gives extra value 🤔

[bmish]

It's required actually. This object stores default values for each config option. These default values are used throughout the codebase. When they have inexact types (i.e. could be one of several types), they won't be able to be used easily due to type mismatches. For example, for an option with an array default value, we won't be able to handle/iterate the default value properly if the type says it could also be a string, boolean, etc.