Migrate from `typed-scss-modules` or find a way to bump its internal dependencies.

[valerybugakov]

Because of the outdated PostCSS plugins, we cannot correctly generate TS types for pseudo selectors in CSS modules.

See related issues and PRs:

• https://github.com/sourcegraph/sourcegraph/pull/46106
• chore: upgrade node-sass, change css-modules-loader-core skovy/typed-scss-modules#166
• update postcss to version 7 css-modules/css-modules-loader-core#231