Problem: simple-network-setup page getting long (#2464)

Solution: Start refactoring it into a new section

docs/server/source/index.rst

@@ -12,7 +12,7 @@ BigchainDB Server Documentation
    ← Back to All BigchainDB Docs <https://docs.bigchaindb.com/en/latest/index.html>
    introduction
    quickstart
-   simple-network-setup
+   network-operations/index
    production-nodes/index
    clusters
    dev-and-test/index

docs/server/source/network-operations/index.rst

@@ -0,0 +1,12 @@
+
+.. Copyright BigchainDB GmbH and BigchainDB contributors
+   SPDX-License-Identifier: (Apache-2.0 AND CC-BY-4.0)
+   Code is Apache-2.0 and docs are CC-BY-4.0
+
+How to Set Up and Run a BigchainDB Network
+==========================================
+
+.. toctree::
+   :maxdepth: 1
+
+   network-setup