[Feature] Various Config file improvements (env vars, better lint…)

[AliSoftware]

Various ideas to improve swiftgen.yml a bit:

• Get inspiration from https://github.com/realm/SwiftLint/pull/1703/files to expand ENV vars from inside the swiftgen.yml file
• Allow wildcards in paths (glob patterns at least, like Resources/**/*.lproj/*.strings?)
• Use a simple command-line argument (instead of a --config option) to specify an alternate config file. E.g. make it be swiftgen config run swiftgen-config.yml instead of swiftgen config run --config swiftgen-config.yml
• Make swiftgen config lint warn about invalid keys

[Lutzifer]

@AliSoftware

Are there any news on the "expand Env Vars" feature?

[AliSoftware]

@Lutzifer haven't found the time to implement it yet, nope 😅

Actually I think it could be a nice starter PR, given that a similar code exists for SwiftLint (see link) so it's more or less a matter of duplicating and adapting that SwiftLint code to SwiftGen 😉 so feel free to give it a try if you are willing 😜

[Lutzifer]

I'll try to have a closer look on of the next weekends.