I256 asr doc (#1860)

* Update I256 documentation to call out diversions from standard numeric types on the right shift operator

* Update changelog

* Address review comment. Link changelog notes to PR

Co-authored-by: Dave Belvedere <dave@protonmail.com>

CHANGELOG.md

@@ -94,6 +94,8 @@
 -   [#1634](https://github.com/gakonst/ethers-rs/pull/1634) Derive missing `Clone`, `Copy` and `Debug` impls in ethers-etherscan.
 -   Bytes debug format now displays hex literals [#1658](https://github.com/gakonst/ethers-rs/pull/1658)
 -   [#1451](https://github.com/gakonst/ethers-rs/issues/1451) Add Arithemtic Shift Left operation for I256
+-   [#1860](https://github.com/gakonst/ethers-rs/pull/1860)Update I256 type documentation calling out the inconsistency 
+    between its right shift operator and standard library numeric types.
 
 ## ethers-contract-abigen
 

ethers-core/src/types/i256.rs

@@ -89,6 +89,12 @@ impl Sign {
 }
 
 /// Little-endian 256-bit signed integer.
+///
+/// ## Diversion from standard numeric types
+/// The right shift operator on I256 doesn't act in the same manner as standard numeric types
+/// (e.g. `i8`, `i16` etc). On standard types if the number is negative right shift will perform
+/// an arithmetic shift, whereas on I256 this will perform a bit-wise shift.
+/// Arithmetic shift on I256 is done via the [asr](I256::asr) and [asl](I256::asl) functions.
 #[derive(Clone, Copy, Default, Deserialize, Eq, Hash, PartialEq, Serialize)]
 #[serde(transparent)]
 pub struct I256(U256);