Fix type error caused by module augmentation

[sapphi-red]

This PR fixes the following type error which happens in v9+.

Module 'postcss-modules/loader' resolves to an untyped module at '/home/projects/node-zgfdsl1t/node_modules/.pnpm/postcss-modules@9.0.0_postcss@8.5.16/node_modules/postcss-modules/build/loader.mjs', which cannot be augmented.

54 declare module "postcss-modules/loader" {}
                  ~~~~~~~~~~~~~~~~~~~~~~~~

Reproduction: https://stackblitz.com/edit/node-zgfdsl1t?file=index.ts,package.json&terminal=test

refs #169

[madyankin]

@sapphi-red thanks! released