Update Changelog.md (#3423)

Changelog.md

@@ -1,34 +1,41 @@
 # Motoko compiler changelog
 
+## 0.6.31 (FUTURE, 2022-08-25)
+
 * motoko (`moc`)
 
   * Adds new syntax for merging records (objects) and
     adding/overwriting fields. The expression
-	`{ baseA and baseB with field1 = val1; field2 = val2 }`
+    ``` motoko
+    { baseA and baseB with field1 = val1; field2 = val2 }
+    ```
     creates a new record by joining all (statically known) fields from
     `baseA/B` and the explicitly specified `field1/2`.
-    Restrictions for ambiguous and `var` fields from bases apply (#3084)
+    This is a _breaking change_, as a new keyword `with` has been added.
+    Restrictions for ambiguous and `var` fields from bases apply. (#3084)
 
   * Add new support for installing actor class instances on the IC,
-    supporting specification of canister settings, install, upgrade and
+    enabling specification of canister settings, install, upgrade and
     reinstall. (#3386)
 
     A new expression
 
-    ```bnf
+    ``` bnf
       (system <exp> . <id>)
     ```
     where `<exp>` is an imported library and `<id>` is the name of
     an actor class, accesses a secondary constructor of the class
     that takes an additional argument controlling the installation.
 
     For example,
-    ```motoko
+    ``` motoko
       await (system Lib.Node)(#upgrade a)(i);
     ```
     upgrades actor `a` with the code for a new instance of class `Lib.Node`,
     passing constructor argument `(i)`.
 
+  * Performance improvements for assigment-heavy code (thanks to nomeata) (#3406)
+
 ## 0.6.30 (2022-08-11)
 
 * motoko (`moc`)