build(deps): bump @docusaurus/core in /website

Bumps [@docusaurus/core](https://github.com/facebook/docusaurus/tree/HEAD/packages/docusaurus) from 2.0.0-beta.14 to 2.0.0-beta.15.
- [Release notes](https://github.com/facebook/docusaurus/releases)
- [Changelog](https://github.com/facebook/docusaurus/blob/main/CHANGELOG.md)
- [Commits](https://github.com/facebook/docusaurus/commits/v2.0.0-beta.15/packages/docusaurus)

---
updated-dependencies:
- dependency-name: "@docusaurus/core"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

website/package.json

@@ -18,7 +18,7 @@
     "ci": "start-server-and-test 'yarn start-server' '3000|3001' 'yarn run cypress run'"
   },
   "dependencies": {
-    "@docusaurus/core": "^2.0.0-beta.14",
+    "@docusaurus/core": "^2.0.0-beta.15",
     "@docusaurus/preset-classic": "^2.0.0-beta.14",
     "@mdx-js/react": "^1.6.21",
     "@svgr/webpack": "^6.2.0",