ignorePatterns and nested configs

[aaronadamsCA]

I'm basically just hoping you can steal this feature from TypeScript:

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-5-5.html#the-configdir-template-variable-for-configuration-files

TypeScript 5.5 introduces a new template variable ${configDir}. When ${configDir} is written in certain path fields of a tsconfig.json or jsconfig.json files, this variable is substituted with the containing directory of the configuration file in a given compilation. This means that the above tsconfig.base.json could be rewritten as:

{
    "compilerOptions": {
        "typeRoots": [
            "${configDir}/node_modules/@types",
            "${configDir}/custom-types"
        ],
        "outDir": "${configDir}/dist"
    }
}

Now, when a project extends this file, the paths will be relative to the derived tsconfig.json, not the shared tsconfig.base.json file. This makes it easier to share configuration files across projects and ensures that the configuration files are more portable.

This would ease migration from eslint.config.ts files.

[aaronadamsCA]

(Currently extends does not extend ignorePatterns, but maybe it could if something like this was available.)