Add Italian Flutter course (EbookFoundation#9949)

Author: mcicolella

Diff for: courses/free-courses-it.md

@@ -229,6 +229,7 @@
 
 * [Computer grafica 2017/2018](https://www.youtube.com/playlist?list=PLUFFnpJdi99kXjntQ0LNPnLbRLjKzmQaC) - A. Bottino, Politecnico di Torino
 * [Corso CSS 3 Completo 2023](https://www.youtube.com/playlist?list=PLP5MAKLy8lP-a0MG-MFHKCISmj2Wg4vT6) - Edoardo Midali
+* [Corso Flutter 2020](https://www.youtube.com/playlist?list=PLFD-5ZFcEgYX5q5pobSkQGfC6rMYy_puq) - Angelo Cassano
 * [Corso HTML 5 Completo 2023](https://www.youtube.com/playlist?list=PLP5MAKLy8lP8U-yYn6J4hGfcee4Tirieg) - Edoardo Midali
 * [Corso HTML 5 Italiano 2023](https://www.youtube.com/playlist?list=PL6PilnEO6HWbTXL8nLSkp-875H-x-vhEo) - Manuel Ricci
 * [Corso SEO Italiano 2023](https://www.youtube.com/playlist?list=PLP5MAKLy8lP9OpFQyF2LnTWgtcoDLgYm7) - Edoardo Midali