Bump postcss-cli from 8.3.0 to 8.3.1 in /build/javascript (#449)

Bumps [postcss-cli](https://github.com/postcss/postcss-cli) from 8.3.0 to 8.3.1.
- [Release notes](https://github.com/postcss/postcss-cli/releases)
- [Changelog](https://github.com/postcss/postcss-cli/blob/master/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss-cli/compare/8.3.0...8.3.1)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build/javascript/package.json

@@ -16,7 +16,7 @@
   },
   "devDependencies": {
     "cssnano": "^4.1.10",
-    "postcss-cli": "^8.3.0"
+    "postcss-cli": "^8.3.1"
   },
   "snowpack": {
     "install": [