Bump gatsby and related dependencies (#378)

This bumps Gatsby and related dependencies to the latest versions. This
resolves some security issues in the dependencies.

Author: Mrtenz

packages/site/package.json

@@ -43,9 +43,9 @@
     "@types/react-dom": "^18.0.6",
     "@types/styled-components": "^5.1.25",
     "eslint": "^9.11.0",
-    "gatsby": "^5.13.3",
-    "gatsby-plugin-manifest": "^5.13.1",
-    "gatsby-plugin-styled-components": "^6.13.1",
+    "gatsby": "^5.14.5",
+    "gatsby-plugin-manifest": "^5.14.0",
+    "gatsby-plugin-styled-components": "^6.14.0",
     "gatsby-plugin-svgr": "^3.0.0-beta.0",
     "rimraf": "^3.0.2",
     "typescript": "~5.7.3"