Add Changelog entries

Changelog.md

@@ -7,8 +7,11 @@ Language Features:
 
 
 Compiler Features:
+ * Constant Optimizer: Uses ``PUSH0`` if supported by the selected evm version.
  * Error Reporting: Unimplemented features are now properly reported as errors instead of being handled as if they were bugs.
  * EVM: Support for the EVM version "Prague".
+ * Peephole Optimizer: ``PUSH0``, when supported, is duplicated explicitly instead of using ``DUP1``.
+ * Peephole optimizer: Remove identical code snippets that terminate the control flow if they occur one after another.
  * SMTChecker: Add CHC engine check for underflow and overflow in unary minus operation.
  * SMTChecker: Replace CVC4 as a possible BMC backend with cvc5.
  * Yul Optimizer: The optimizer now treats some previously unrecognized identical literals as identical.