Revise roadmap title and status

Updated the roadmap title and clarified its status as 'in preparation'.

Author: mchaamsler

docs/general/roadmap.md

@@ -1,9 +1,9 @@
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-sidebar_position: ...
+sidebar_position: 8
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-# Roadmap
-This is the current **roadmap** of our Open Data service, which will guide us until the end of 2026.
+# Roadmap (in preparation)
+This is the current **roadmap** (*in preparation*) of our Open Data service, which will guide us until the end of 2026.
 - It is iterated on at least a quarterly basis.
 - It allows us to plan for change. It captures intent, not solutions. The further into the future a mission will take place, the more uncertain it is. 
 - Things can be added to or dropped from the roadmap. In the latter case, we document this below under ‘Items removed from the roadmap’, including the date and reason.