Added Swift podcast (#8556)

* Added Swift podcast

* Fix md syntax

* Fix formatting 

Add extra space between last link and heading.

* Fixed typo

casts/free-podcasts-screencasts-en.md

@@ -31,6 +31,7 @@
 * [Python](#python)
 * [Ruby](#ruby)
 * [Rust](#rust)
+* [Swift](#swift)
 
 
 ### Android
@@ -397,3 +398,8 @@
 * [New Rustacean](http://www.newrustacean.com) - Chris Krycho (podcast)
 * [Rusty Radio](https://soundcloud.com/posix4e) - Alex Newman (podcast)
 * [The Rustacean Station Podcast](https://rustacean-station.org) - Allen Wyma, Tim McNamara, Sean Chen, et al. (podcast)
+
+
+### Swift
+
+* [Swift by Sundell](https://www.swiftbysundell.com/podcast/) - John Sundell (podcast)