Add beacon proxy changelog entry

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+ * Add beacon proxy. ([#2411](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2411))
+
+## Unreleased
+
  * Now supports both Solidity 0.6 and 0.7. Compiling with solc 0.7 will result in warnings. Install the `solc-0.7` tag to compile without warnings.
  * `Address`: added `functionStaticCall` and `functionDelegateCall`, similar to the existing `functionCall`. ([#2333](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2333))
  * `TimelockController`: added a contract to augment access control schemes with a delay. ([#2354](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2354))