import { type ExtractSpecifier } from "https://deno.land/x/format@1.1.0/mod.ts";
Extract specifier(string that enclosed by Placeholder) from T.
Type Parameters
U extends Placeholder
definition: U extends U ? T extends `${infer R}${U["prefix"]}${infer P}${U["suffix"]}${infer R}` ? P | ExtractSpecifier<R, U> : never : never