update README

pkg/scale/README.md

@@ -77,6 +77,39 @@ SCALE uses a compact encoding for variable width unsigned integers.
 | `Compact<u64>`      | `uint`                  |
 | `Compact<u128>`     | `*big.Int`              |
 
+### BitVec
+
+SCALE uses a bit vector to encode a sequence of booleans.  The bit vector is encoded as a compact length followed by a byte array.  
+The byte array is a sequence of bytes where each bit represents a boolean value.
+
+**Note: This is a work in progress.**
+The current implementation of BitVec is just bare bones.  It does not implement any of the methods of the `BitVec` type in Rust.
+
+```go
+import (
+    "fmt"
+    "github.com/ChainSafe/gossamer/pkg/scale"
+)
+
+func ExampleBitVec() {
+	bitvec := NewBitVec([]bool{true, false, true, false, true, false, true, false})
+	bytes, err := scale.Marshal(bitvec)
+	if err != nil {
+        panic(err)
+    }
+
+	var unmarshaled BitVec
+	err = scale.Unmarshal(bytes, &unmarshaled)
+	if err != nil {
+        panic(err)
+    }
+
+	// [true false true false true false true false]
+	fmt.Printf("%v", unmarshaled.Bits())
+}
+```
+
+
 ## Usage
 
 ### Basic Example