Moves config for new users into a .config folder per #33

[lleadbet]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Problem/Feature

Per feedback in #33, this PR moves new installation's configurations to a .config subdirectory; existing users are unaffected.

Description of Changes:

• Defaults the path to $HOME/.config/.twitch-cli

Checklist

• My code follows the Contribution Guide
• I have self-reviewed the changes being requested
• I have made comments on pieces of code that may be difficult to understand for other editors
• I have updated the documentation (if applicable)

[zneix]

Good job so far, looking forward to have this merged in 👍 I've got a couple things to point out though

1. I believe that this PR should also take XDG_CONFIG_HOME into account and use it instead of ".config" if the mentioned environment variable exists.
2. How would this act on Windows? I believe that should use %APPDATA%'s value instead of ".config", since that's the closest equivalent of .config on Windows.

I've recently done similar work with implementing viper respecting XDG standard to a project I collaborate on. Guessing it might be helpful a little, so here it is: https://github.com/Chatterino/api/blob/d6d80e88538bf75af022e487aef6ffb81c0548eb/pkg/config/config.go#L84-L103

[lleadbet]

Good job so far, looking forward to have this merged in 👍 I've got a couple things to point out though

1. I believe that this PR should also take XDG_CONFIG_HOME into account and use it instead of ".config" if the mentioned environment variable exists.
2. How would this act on Windows? I believe that should use %APPDATA%'s value instead of ".config", since that's the closest equivalent of .config on Windows.

I've recently done similar work with implementing viper respecting XDG standard to a project I collaborate on. Guessing it might be helpful a little, so here it is: https://github.com/Chatterino/api/blob/d6d80e88538bf75af022e487aef6ffb81c0548eb/pkg/config/config.go#L84-L103

Appreciate it; currently it would just tuck it in a .config folder on Windows; but agree $APPDATA might be a good fit; might use some of that code since it is pretty similar to what we'd like to achieve.