Add course related to a Julia package about measuring uncertainty (#8193)

* Add course related to a Julia package about measuring uncertainty

* Fix ordering issue

* Remove YouTube attribute

courses/free-courses-en.md

@@ -831,6 +831,7 @@
 
 ### Julia
 
+* [Decision Making Under Uncertainty using POMDPs.jl](https://www.youtube.com/playlist?list=PLP8iPy9hna6QPqk4N8eBk0oXzLrLbOtTA) - The Julia Programming Language
 * [GeoStats.jl Tutorials](https://www.youtube.com/playlist?list=PLsH4hc788Z1f1e61DN3EV9AhDlpbhhanw) - Julio Hoffimann (YouTube)
 * [Julia Tutorials (Basic)](https://www.youtube.com/playlist?list=PLP8iPy9hna6SCcFv3FvY_qjAmtTsNYHQE) - The Julia Programming Language (YouTube)