Update docusaurus to 2.0.0-rc.1 (#1224)

Author: lwronski

website/package.json

@@ -14,8 +14,8 @@
     "write-heading-ids": "docusaurus write-heading-ids"
   },
   "dependencies": {
-    "@docusaurus/core": "2.0.0-beta.20",
-    "@docusaurus/preset-classic": "2.0.0-beta.20",
+    "@docusaurus/core": "2.0.0-rc.1",
+    "@docusaurus/preset-classic": "2.0.0-rc.1",
     "@mdx-js/react": "^1.6.22",
     "clsx": "^1.1.1",
     "docusaurus-plugin-sass": "^0.2.2",