Load .env files when launching from CLI

[claytercek]

resolves #53

• added support for .env files
• updated documentation to reflect .env support and deprecate crendentials file
• refactored config loading logic to allow loading the env between finding the config and loading the config
• added additional CLI options for specifying env files

I refactored the ConfigManager to just be a couple of exported functions from config.js, as now that it's not a singleton, basically all of the methods were just static anyways.

[claytercek]

Tested this a bit more thoroughly, it feels stable to me!

I pulled any recommendation for using credentials.json from the docs, replacing it with .env examples and instructions, and noted credentialsPath as deprecated in the config options.

[benjaminbojko]

This looks great! Thanks for the PR. Only had one question about loadConfig() as defined in .docs/generate.mjs. Looks like maybe that's a relic?

Also, should we explicitly mark credentials.js as deprecated (the class and constructor itself)?

Great addition to the library, and will offer a lot more flexibility.

[benjaminbojko]

Great! This looks good to merge to me. @claytercek Do you think we're at a good point to publish to NPM now? Also wondering if this actually constitutes to a minor change for all packages (minus scaffold) instead of just a patch at this point.

[claytercek]

Deprecated the Credentials class and all its methods. Unfortunately, there's no way to mark the credentialsPath property in the content config options as deprecated with jsDoc, so I just noted it in the description.

[claytercek]

Oh yeah, this probably makes more sense as a minor change. I'll update that and merge.

I think once this is merged it would be in a good spot to publish!