Create a SnakeCase<T> generic that turns a string formatted in camelCase into a string formatted in snake_case.
A few examples:
type res1 = SnakeCase<"hello">; // => "hello"
type res2 = SnakeCase<"userName">; // => "user_name"
type res3 = SnakeCase<"getElementById">; // => "get_element_by_id"
import type { Equal, Expect } from '@type-challenges/utils'
type cases = [
Expect<Equal<SnakeCase<'hello'>, 'hello'>>,
Expect<Equal<SnakeCase<'userName'>, 'user_name'>>,
Expect<Equal<SnakeCase<'getElementById'>, 'get_element_by_id'>>,
Expect<Equal<SnakeCase<'getElementById' | 'getElementByClassNames'>, 'get_element_by_id' | 'get_element_by_class_names'>>,
]