[TASK] Activate all required extensions

This change modifies the `QuickStart: Set up TYPO3`
section to activate the mandantory system extension
`indexed_search` along with `styleguide` to reflect latest
dependency chain.

Documentation/Quickstart/5-TYPO3.rst

@@ -67,6 +67,7 @@ Quick Start: Set up TYPO3
         :caption: **Ensure extension setup and activate EXT:styleguide**
 
         ddev typo3 extension:setup && \
+            ddev typo3 extension:activate indexed_search && \
             ddev typo3 extension:activate styleguide
 
     ..  code:: bash