Add shared tycho-substreams lib.

crates/tycho-substreams/Readme.md

@@ -0,0 +1,18 @@
+# Tycho Substreams SDK
+
+Some shared functionality that is used to create tycho substream packages.
+
+## Protobuf Models
+
+Protobuf models are manually synced from the `tycho-indexer` repository whenever they 
+changed.
+
+To generate the rust structs run the following command from within the `./proto` 
+directory:
+
+```bash
+buf generate \
+  --path tycho \
+  --template ../crates/tycho-substreams/buf.gen.yaml \
+  --output ../crates/tycho-substreams/ 
+```