feat: support flat config

[sxzz]

docs: https://eslint.org/docs/latest/user-guide/configuring/configuration-files-new

closes #122

[Shinigami92]

@sxzz I'm not sure about the term legacy 🤔
Is it coming from ESLint? Or did you came up with this term?

[sxzz]

@Shinigami92 According to the blog, I think flat config is the future. Actually, I'm not sure, but it has to get a name. What name do you prefer?
legacy, nested, or something else?

[Shinigami92]

@Shinigami92 According to the blog, I think flat config is the future. Actually, I'm not sure, but it has to get a name. What name do you prefer? legacy, nested, or something else?

Ah yeah, then I'm against legacy as it indicates now as it would be deprecated, but it is not. The new FlatConfig is just the new way for now.

For now I wouldn't change it at all and just stick with config and flat-config and use this terminology the whole way down.
Like ESLintConfig and FlatESLintConfig and so on.

... And oh yeah, please use FlatESLintConfig instead of ESLintFlatConfig as this is what they call it:

[sxzz]

@Shinigami92 I agree with you. I will change it

[Shinigami92]

I have some Meetings and Company Work today, if I find the time this evening, I will release your (welcome 🤗) additions 👍
(I'm in German TimeZone)

[sxzz]

@Shinigami92 OK thanks~