chore: update changelog

CHANGELOG.md

@@ -1,3 +1,13 @@
+## 2.0.0
+
+ - fix!: `push` & `unshift` now accept `undefined` values to match behaviour of `Array` (fixes #25) (#35)
+   - This is only a **BREAKING** change if you are currently expecting `push(undefined)` and `unshift(undefined)` to do
+     nothing - the new behaviour now correctly adds undefined values to the queue.
+   - **Note**: behaviour of `push()` & `unshift()` (no arguments) remains unchanged (nothing gets added to the queue).
+   - **Note**: If you need to differentiate between `undefined` values in the queue and the return value of `pop()` then
+     check the queue `.length` before popping.
+ - fix: incorrect methods in types definition file
+
 ## 1.5.1
 
  - perf: minor performance tweak when growing queue size (#29)