split data in separate files

docs/goods/timber.md

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+# Timber (Planks)
+
+**Entity Type:** Good
+
+## Properties
+
+| Field | Value |
+|-------|-------|
+| Category | Construction Material |
+| Used For | Construction, Inputs |
+
+## Production
+
+**Produced By:** [Sawmill](../buildings/sawmill.md)
+
+**Consumed By:** Many buildings (construction costs reference Timber widely)
+
+## Related Chain
+
+[Timber Chain](../production-chains/timber.md)