Update CHANGELOG.md for Swift 5.3 release (swiftlang#33974)

<https://swift.org/blog/swift-5-3-released/>

Author: benrimmington

CHANGELOG.md

@@ -4,24 +4,23 @@ CHANGELOG
 <details>
 <summary>Note: This is in reverse chronological order, so newer entries are added to the top.</summary>
 
-| Version                   | Released   | Toolchain   |
-| :------------------------ | :--------- | :---------- |
-| [Swift Next](#swift-next) |
-| [Swift 5.3](#swift-53)    | 2020-09-16 | Xcode 12.0  |
-| [Swift 5.2](#swift-52)    | 2020-03-24 | Xcode 11.4  |
-| [Swift 5.1](#swift-51)    | 2019-09-20 | Xcode 11.0  |
-| [Swift 5.0](#swift-50)    | 2019-03-25 | Xcode 10.2  |
-| [Swift 4.2](#swift-42)    | 2018-09-17 | Xcode 10.0  |
-| [Swift 4.1](#swift-41)    | 2018-03-29 | Xcode 9.3   |
-| [Swift 4.0](#swift-40)    | 2017-09-19 | Xcode 9.0   |
-| [Swift 3.1](#swift-31)    | 2017-03-27 | Xcode 8.3   |
-| [Swift 3.0](#swift-30)    | 2016-09-13 | Xcode 8.0   |
-| [Swift 2.2](#swift-22)    | 2016-03-21 | Xcode 7.3   |
-| [Swift 2.1](#swift-21)    | 2015-10-21 | Xcode 7.1   |
-| [Swift 2.0](#swift-20)    | 2015-09-17 | Xcode 7.0   |
-| [Swift 1.2](#swift-12)    | 2015-04-08 | Xcode 6.3   |
-| [Swift 1.1](#swift-11)    | 2014-12-02 | Xcode 6.1.1 |
-| [Swift 1.0](#swift-10)    | 2014-09-15 | Xcode 6.0   |
+| Version                | Released   | Toolchain   |
+| :--------------------- | :--------- | :---------- |
+| [Swift 5.3](#swift-53) | 2020-09-16 | Xcode 12.0  |
+| [Swift 5.2](#swift-52) | 2020-03-24 | Xcode 11.4  |
+| [Swift 5.1](#swift-51) | 2019-09-20 | Xcode 11.0  |
+| [Swift 5.0](#swift-50) | 2019-03-25 | Xcode 10.2  |
+| [Swift 4.2](#swift-42) | 2018-09-17 | Xcode 10.0  |
+| [Swift 4.1](#swift-41) | 2018-03-29 | Xcode 9.3   |
+| [Swift 4.0](#swift-40) | 2017-09-19 | Xcode 9.0   |
+| [Swift 3.1](#swift-31) | 2017-03-27 | Xcode 8.3   |
+| [Swift 3.0](#swift-30) | 2016-09-13 | Xcode 8.0   |
+| [Swift 2.2](#swift-22) | 2016-03-21 | Xcode 7.3   |
+| [Swift 2.1](#swift-21) | 2015-10-21 | Xcode 7.1   |
+| [Swift 2.0](#swift-20) | 2015-09-17 | Xcode 7.0   |
+| [Swift 1.2](#swift-12) | 2015-04-08 | Xcode 6.3   |
+| [Swift 1.1](#swift-11) | 2014-12-02 | Xcode 6.1.1 |
+| [Swift 1.0](#swift-10) | 2014-09-15 | Xcode 6.0   |
 
 </details>
 
@@ -80,9 +79,13 @@ Swift Next
   let _: Foo? = .bar.anotherFoo.getFoo().optionalFoo?.optionalFoo![]
   ```
 
+**Add new entries to the top of this section, not here!**
+
 Swift 5.3
 ---------
 
+### 2020-09-16 (Xcode 12.0)
+
 * [SE-0279][] & [SE-0286][]:
 
   Trailing closure syntax has been extended to allow additional labeled closures to follow the initial unlabeled closure: