build(deps-dev): bump postcss-import from 14.1.0 to 15.1.0 in /docs

Bumps [postcss-import](https://github.com/postcss/postcss-import) from 14.1.0 to 15.1.0.
- [Release notes](https://github.com/postcss/postcss-import/releases)
- [Changelog](https://github.com/postcss/postcss-import/blob/master/CHANGELOG.md)
- [Commits](postcss/postcss-import@14.1.0...15.1.0)

---
updated-dependencies:
- dependency-name: postcss-import
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

docs/package-lock.json

@@ -15,7 +15,7 @@
     "autoprefixer": "^10.4.7",
     "cross-env": "^7.0.3",
     "dotenv": "^16.0.1",
-    "postcss-import": "^14.1.0",
+    "postcss-import": "^15.1.0",
     "tailwindcss": "^3.1.6",
     "types-quill-delta": "^1.0.0",
     "vitepress": "^1.0.0-alpha.4",