Added course for Beckhoff's TwinCAT 3. (#5517)

* Added course for Beckhoff's TwinCAT 3.

* Fixed spacing to next heading.

* Update courses/free-courses-en.md

Added platform (YouTube)
Co-authored-by: NDavid Ordás <davorpatech@gmail.com>

* Added additional free courses for TwinCAT 3.
Co-authored-by: NDavid Ordás <davorpatech@gmail.com>

courses/free-courses-en.md

@@ -62,6 +62,7 @@
 * [Swift](#swift)
   * [Vapor](#vapor)
 * [Theory](#theory)
+* [TwinCAT 3](#twincat-3)
 * [TypeScript](#typescript)
 * [Verilog / VHDL / SystemVerilog](#verilog--vhdl--systemverilog)
 * [Web Development](#web-development)
@@ -727,6 +728,13 @@
 * [Intro to Theoretical Computer Science](https://www.udacity.com/course/intro-to-theoretical-computer-science--cs313) (Udacity)
 
 
+### TwinCAT 3
+
+* [Learning motion control and IO with Beckhoff TwinCAT PLCs](https://www.youtube.com/playlist?list=PLE1CU6EebvTD29gsHo1djsKU7J5Dtp0Bn) - Evan Jensen (YouTube)
+* [Learning PLCs with Structured Text](https://www.youtube.com/playlist?list=PLE1CU6EebvTCJCMIUOSWgMseMaW-2k5zH) - Evan Jensen (YouTube)
+* [PLC programming using TwinCAT 3](https://www.youtube.com/playlist?list=PLimaF0nZKYHz3I3kFP4myaAYjmYk1SowO) - Jakob Sagatowski (YouTube)
+
+
 ### TypeScript
 
 * [Introduction to TypeScript](https://www.udemy.com/typescript/) - Daniel Stern (Udemy)