Upgrade Prettier from 1.17 to 2.0.2.

Summary:
This gets us on the latest Prettier 2.x:
https://prettier.io/blog/2020/03/21/2.0.0.html

Notably, this adds support for TypeScript 3.8,
which introduces new syntax, such as `import type`.

Reviewed By: zertosh

Differential Revision: D20636268

fbshipit-source-id: fca5833d003804333a05ba16325bbbe0e06d6c8a

website/src/pages/docs/index.js

@@ -49,17 +49,16 @@ export default ({data}) => (
                   ({node}) =>
                     node.fileAbsolutePath.indexOf(`/${category}/`) > -1,
                 )
-                .map(
-                  ({node}) =>
-                    node.frontmatter.redirect ? (
-                      <a key={node.id} href={node.frontmatter.path}>
-                        {node.frontmatter.title}
-                      </a>
-                    ) : (
-                      <Link key={node.id} to={node.frontmatter.path}>
-                        {node.frontmatter.title}
-                      </Link>
-                    ),
+                .map(({node}) =>
+                  node.frontmatter.redirect ? (
+                    <a key={node.id} href={node.frontmatter.path}>
+                      {node.frontmatter.title}
+                    </a>
+                  ) : (
+                    <Link key={node.id} to={node.frontmatter.path}>
+                      {node.frontmatter.title}
+                    </Link>
+                  ),
                 )}
             </Col>
           ),