build(deps): bump @mdx-js/mdx from 1.6.18 to 1.6.22 in /docs (#1624)

Author: dependabot[bot]

docs/package-lock.json

@@ -8,7 +8,7 @@
   "dependencies": {
     "@emotion/core": "^10.1.1",
     "@emotion/styled": "^10.0.27",
-    "@mdx-js/mdx": "^1.6.18",
+    "@mdx-js/mdx": "^1.6.22",
     "@mdx-js/react": "^1.6.16",
     "emotion-theming": "^10.0.27",
     "gatsby": "^2.29.3",