Plug NetBox Cloud in installation docs

Author: jeremystretch

docs/installation/index.md

@@ -1,5 +1,8 @@
 # Installation
 
+!!! info "NetBox Cloud"
+    The instructions below are for installing NetBox as a standalone, self-hosted application. For a Cloud-delivered solution, check out [NetBox Cloud](https://netboxlabs.com/netbox-cloud/) by NetBox Labs.
+
 The installation instructions provided here have been tested to work on Ubuntu 22.04 and CentOS 8.3. The particular commands needed to install dependencies on other distributions may vary significantly. Unfortunately, this is outside the control of the NetBox maintainers. Please consult your distribution's documentation for assistance with any errors.
 
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