bring blockchain back

spec/blockchain/blockchain.md

@@ -0,0 +1,3 @@
+# Blockchain
+
+Deprecated see [core/data_structures.md](../core/data_structures.md)

spec/blockchain/encoding.md

@@ -0,0 +1,3 @@
+# Encoding
+
+Deprecated see [core/data_structures.md](../core/encoding.md)

spec/blockchain/readme.md

@@ -0,0 +1,11 @@
+---
+cards: false
+---
+
+# Blockchain
+
+This section describes the core types and functionality of the Tendermint protocol implementation.
+
+[Core Data Structures](./data_structures.md)
+[Encoding](./encoding.md)
+[State](./state.md)

spec/blockchain/state.md

@@ -0,0 +1,3 @@
+# State
+
+Deprecated see [core/state.md](../core/state.md)