Bump @docusaurus/core from 2.0.0-alpha.65 to 2.0.0-beta.9

Bumps [@docusaurus/core](https://github.com/facebook/docusaurus/tree/HEAD/packages/docusaurus) from 2.0.0-alpha.65 to 2.0.0-beta.9.
- [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.9/packages/docusaurus)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package.json

@@ -9,7 +9,7 @@
     "deploy": "docusaurus deploy"
   },
   "dependencies": {
-    "@docusaurus/core": "2.0.0-alpha.65",
+    "@docusaurus/core": "2.0.0-beta.9",
     "@docusaurus/preset-classic": "2.0.0-alpha.65",
     "classnames": "^2.3.1",
     "react": "^16.14.0",