feat(substreams): add substreams for Uniswap v2 and v3

substreams/crates/substreams-helper/src/hex.rs

@@ -0,0 +1,20 @@
+use ethabi::ethereum_types::Address;
+use substreams::Hex;
+
+pub trait Hexable {
+    fn to_hex(&self) -> String;
+}
+
+impl Hexable for Vec<u8> {
+    fn to_hex(&self) -> String {
+        let mut str = Hex::encode(self);
+        str.insert_str(0, "0x");
+        str
+    }
+}
+
+impl Hexable for Address {
+    fn to_hex(&self) -> String {
+        self.as_bytes().to_vec().to_hex()
+    }
+}