Merge pull request plone#1356 from plone/landing-page

Add intro landing page

Author: ksuess

docs/index.md

@@ -11,7 +11,20 @@ myst:
 
 # Plone 6 Documentation
 
-This website is the HTML documentation of Plone, an open source, enterprise-level content management system.
+This is the community-maintained documentation for the Plone content management system.
+
+This documentation is for:
+
+- Editors who write and update content on a site
+- Site administrators who install Plone and add-ons, and set up a site
+- Designers who create site themes
+- Deployers who configure servers for site hosting
+- Developers who customize a site’s capabilities, create add-ons, and contribute to Plone itself
+
+```{seealso}
+Read the [documentation for the previous version, Plone 5](https://docs.plone.org/).
+```
+
 
 ```{toctree}
 :maxdepth: 2