Podcast and course sources were added for Turkish and English content. (#6207)

* podcast and course sources were added for turkish and english content.

* alphabetic order for the course of Turkish.

* marking configuration were edited and it's valid for the project.

* stackoverflow podcast link was changed.

* turkish podcast link was changed. turkish course content order was changed. html-css section merged. the name of two section changed as ide-editor and version control systems.

* trendyol podcast link changed.

* removing trailing slash of the trendyol podcast link.

casts/free-podcasts-screencasts-en.md

@@ -270,6 +270,7 @@
 * [The Path to Performance](https://pathtoperf.com) (podcast)
 * [The Podcast from DZone.com: "For Developers, by Developers"](https://soundcloud.com/john-esposito-23072673) (podcast)
 * [The Silver Bullet Security Podcast with Gary McGraw](http://www.computer.org/web/computingnow/silverbullet) (podcast)
+* [The Stack Overflow Podcast](https://stackoverflow.blog/podcast/) (podcast)
 * [The Web Ahead](http://5by5.tv/webahead) (podcast)
 * [The Web Platform](http://thewebplatform.libsyn.com) (podcast)
 * [Thinking with Tanay](https://anchor.fm/tanaypratap) (podcast)

casts/free-podcasts-screencasts-tr.md

@@ -9,6 +9,7 @@
 * [codefiction](https://codefiction.tech) (podcast)
 * [devPod](https://devpod.org) (screencast)
 * [kodpod](https://kodpod.live) (podcast)
+* [Trendyol Tech Podcasts](https://trendyol.simplecast.com) (podcast)
 
 
 ### JavaScript