[Feature Request] Update `ESLint` version and migrate config to `Flat Config` format

[filzrev]

Is your feature request related to a problem? Please describe.

When running npm install command on templtes directory. Following warnings are displayed.

npm warn deprecated inflight@1.0.6: This module is not supported, and leaks memory. Do not use it. Check out lru-cache if you want a good and tested way to coalesce async requests by a key value, which is much more comprehensive and powerful.
npm warn deprecated @humanwhocodes/config-array@0.13.0: Use @eslint/config-array instead
npm warn deprecated rimraf@3.0.2: Rimraf versions prior to v4 are no longer supported
npm warn deprecated glob@7.2.3: Glob versions prior to v9 are no longer supported
npm warn deprecated @humanwhocodes/object-schema@2.0.3: Use @eslint/object-schema instead
npm warn deprecated eslint@8.57.1: This version is no longer supported. Please see https://eslint.org/version-support for other options.

These packages are used by eslint@8.57.1. So it need to update eslint version. But it seems eslint-config-standard package has no compatible to eslint 9.0, (https://github.com/standard/eslint-config-standard/issues/410)

Describe the solution you'd like

• Remove eslint-config-standard rules (temporary)
• Update ESLint version to 9.x.
• Update ESLint config to use Flat Config format

[!NOTE] ESLint 9 changes default configuration system to Flat Config Existing config file (.stylelintrc.json) supports are expected to be dropped in future.