Fix relative links

Summary: Translated all cases where we had a parent-relative link to use the base URL instead.

Reviewed By: jknoxville

Differential Revision: D22256229

fbshipit-source-id: 81ee6fecb77dbaa19d112cb319771c22ff66d02a

docs/features/databases-plugin.mdx

@@ -3,8 +3,9 @@ id: databases-plugin
 title: Databases
 ---
 import useBaseUrl from '@docusaurus/useBaseUrl';
+import Link from '@docusaurus/Link';
 
-→ [See setup instructions for the Databases plugin](../setup/databases-plugin)
+→ <Link to={useBaseUrl("/docs/setup/databases-plugin")}>See setup instructions for the Databases plugin</Link>
 
 The Databases plugin provides developers with read-write access to their databases:
 - browse your tables' data