build(deps): bump postcss from 8.5.6 to 8.5.15 in /frontend (#691)

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.6 to 8.5.15.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.6...8.5.15)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.15
  dependency-type: indirect
...

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

Author: dependabot[bot]

frontend/package-lock.json

@@ -5113,10 +5113,10 @@ nano-spawn@^2.0.0:
   resolved "https://registry.npmjs.org/nano-spawn/-/nano-spawn-2.0.0.tgz"
   integrity sha512-tacvGzUY5o2D8CBh2rrwxyNojUsZNU2zjNTzKQrkgGJQTbGAfArVWXSKMBokBeeg6C7OLRGUEyoFlYbfeWQIqw==
 
-nanoid@^3.3.11:
-  version "3.3.11"
-  resolved "https://registry.npmjs.org/nanoid/-/nanoid-3.3.11.tgz"
-  integrity sha512-N8SpfPUnUp1bK+PMYW8qSWdl9U+wwNWI4QKxOYDy9JAro3WMX7p2OeVRF9v+347pnakNevPmiHhNmZ2HbFA76w==
+nanoid@^3.3.12:
+  version "3.3.12"
+  resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.12.tgz#ab3d912e217a6d0a514f00a72a16543a28982c05"
+  integrity sha512-ZB9RH/39qpq5Vu6Y+NmUaFhQR6pp+M2Xt76XBnEwDaGcVAqhlvxrl3B2bKS5D3NH3QR76v3aSrKaF/Kiy7lEtQ==
 
 napi-postinstall@^0.3.0:
   version "0.3.4"
@@ -5503,11 +5503,11 @@ postcss-value-parser@^4.2.0:
   integrity sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==
 
 postcss@^8.5.1, postcss@^8.5.6:
-  version "8.5.6"
-  resolved "https://registry.npmjs.org/postcss/-/postcss-8.5.6.tgz"
-  integrity sha512-3Ybi1tAuwAP9s0r1UQ2J4n5Y0G05bJkpUIO0/bI9MhwmD70S5aTWbXGBwxHrelT+XM1k6dM0pk+SwNkpTRN7Pg==
+  version "8.5.15"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.5.15.tgz#d1eaf677a324e9ec02196da2d3fecf4a0b9a735c"
+  integrity sha512-FfR8sjd4em2T6fb3I2MwAJU7HWVMr9zba+enmQeeWFfCbm+UOC/0X4DS8XtpUTMwWMGbjKYP7xjfNekzyGmB3A==
   dependencies:
-    nanoid "^3.3.11"
+    nanoid "^3.3.12"
     picocolors "^1.1.1"
     source-map-js "^1.2.1"