Release infra: release ent diagram updated using mermaid

Summary:
Updated the release ent diagram using mermaid lib added in the previous diff.

nocommit until "docusaurus-plugin-internaldocs-fb" re-pointed back to npm in package.json.

Reviewed By: jknoxville

Differential Revision: D25594333

fbshipit-source-id: fd0b961c5265b8284d3c2e56e17b56fc38cc72c5

website/src/theme/Mermaid.js

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import React, { useEffect } from "react"
+import mermaid from "mermaid"
+
+mermaid.initialize({
+  startOnLoad: true
+})
+
+/*
+Use in *.mdx like:
+
+ import Mermaid from '@theme/Mermaid'
+ <Mermaid chart={`
+ flowchart TD
+     cr([Create Request]) --> backoffice[Backoffice Server REST]
+ `}/>
+*/
+const Mermaid = ({ chart }) => {
+  useEffect(() => {
+    mermaid.contentLoaded()
+  }, [])
+  return <div className="mermaid">{chart}</div>
+}
+
+export default Mermaid;