Rewrote the configuration and logic of the defineConfig function
to better resemble a standard ESLint configuration.
Also removing the necessity of a function to detect tsconfig/jsconfig
files.
Fixing ESLint flat-config by default #3.
Created/configured the basic rules, extending eslint and
typescript-eslint recommended rules. Currently these rules are mostly
mimicking [antfu's config](https://github.com/antfu/eslint-config)
