Add zh cast file and excellent podcasts (EbookFoundation#7612)

* Add zh cast file and popular podcasts

* Add zh casts link

* Update cast notations

Author: Kashinggo

README.md

@@ -180,6 +180,7 @@ This project lists books and other resources grouped by genres:
 Free Podcasts and Screencasts:
 
 + [Arabic / al Arabiya / العربية](casts/free-podcasts-screencasts-ar.md)
++ [Chinese / 中文](casts/free-podcasts-screencasts-zh.md)
 + [Czech / čeština / český jazyk](casts/free-podcasts-screencasts-cs.md)
 + [English](casts/free-podcasts-screencasts-en.md)
 + [Finnish / Suomi](casts/free-podcasts-screencasts-fi.md)

casts/free-podcasts-screencasts-zh.md

@@ -0,0 +1,21 @@
+### Index
+
+* [JavaScript](#javascript)
+* [Python](#python)
+* [Swift](#swift)
+
+
+### JavaScript
+
+* [Async Talk](https://asynctalk.com) - AnnatarHe, Sleaf, TinkoQWQ (podcast)
+* [Web Worker 播客](https://www.webworker.tech) - 辛宝Otto, 刘威Franky, 小白菜Cabbage (podcast)
+
+
+### Python
+
+* [捕蛇者说](https://pythonhunter.org) - laike9m, Manjusaka, Ada Wen, laixintao, 小白 (podcast)
+
+
+### Swift
+
+* [weak self podcast](https://weakself.dev) - 一三, 波肥, 喬喬 (podcast)