chore: checkpoint before Python removal

vendor/ecdsa/src/normalized.rs

@@ -0,0 +1,11 @@
+//! Support for ECDSA signatures with low-S normalization.
+
+use crate::Signature;
+use elliptic_curve::PrimeCurve;
+
+/// ECDSA signature with low-S normalization applied.
+#[derive(Clone, Eq, PartialEq)]
+#[repr(transparent)]
+pub struct NormalizedSignature<C: PrimeCurve> {
+    inner: Signature<C>,
+}