Site: Description of the hono playground hono.eclipse.org

Signed-off-by: pellmann <marc.pellmann@bosch-si.com>

site/content/playground.md

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+title = "Playground"
+menu = "main"
+weight = 160
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+
+You find our Eclipse hosted Hono playground under 
+
+`hono.eclipse.org`  
+
+From the browser with port 80 you will be redirected to this documentation page, you are just reading.
+
+### Purpose
+
+The playground hosts a publicly available Hono installation, which consists of the Hono docker installation, as described in the [Getting started]({{< relref "getting-started.md" >}}).
+
+You could use it the same way without the need to install it yourself. The ports for all components are the same.
+
+### Take note
+
+- This is just a **playground**. It could and will be rolled out often and all data will be lost.   
+
+- Devices and credentials could be created but not updated/deleted.
+
+- You should choose a unique tenant name (e.g. a UUID), to be sure you do not interfere with other users on this test installation.