It appears that the repository has undergone several changes and renamings:

backend/node_modules/postcss-nested/index.d.ts

@@ -1,41 +0,0 @@
-// Original definitions (@types/postcss-nested)
-// by Maxim Vorontsov <https://github.com/VorontsovMaxim>
-
-import { PluginCreator } from 'postcss'
-
-declare namespace nested {
-  interface Options {
-    /**
-     * By default, plugin will bubble only `@media`, `@supports` and `@layer`
-     * at-rules. Use this option to add your custom at-rules to this list.
-     */
-    bubble?: string[]
-
-    /**
-     * By default, plugin will unwrap only `@font-face`, `@keyframes`,
-     * and `@document` at-rules. You can add your custom at-rules
-     * to this list by this option.
-     */
-    unwrap?: string[]
-
-    /**
-     * By default, plugin will strip out any empty selector generated
-     * by intermediate nesting levels. You can set this option to `true`
-     * to preserve them.
-     */
-    preserveEmpty?: boolean
-
-    /**
-     * The plugin supports the SCSS custom at-rule `@at-root` which breaks
-     * rule blocks out of their nested position. If you want, you can choose
-     * a new custom name for this rule in your code.
-     */
-    rootRuleName?: string
-  }
-
-  type Nested = PluginCreator<Options>
-}
-
-declare const nested: nested.Nested
-
-export = nested