add The Pharo MOOC (#6241)

* add The Pharo MOOC

* fix formatting for pharo section

* add pharo to index

courses/free-courses-en.md

@@ -52,6 +52,7 @@
 * [.NET](#net)
 * [OCaml](#ocaml)
 * [Perl](#perl)
+* [Pharo](#pharo)
 * [PHP](#php)
 * [PLC - Programmable logic controllers](#plc---programmable-logic-controllers)
 * [Processing](#processing)
@@ -704,6 +705,11 @@
 * [Perl Tutorial](https://www.youtube.com/playlist?list=PL_RGaFnxSHWpqRBcStwV0NwMA3nXMh5GC)
 
 
+### Pharo
+
+* [The Pharo MOOC](https://mooc.pharo.org) - Damien Cassou, Stéphane Ducasse, Luc Fabresse
+
+
 ### PHP
 
 * [Laravel 5.8 Tutorial From Scratch](https://www.youtube.com/playlist?list=PLpzy7FIRqpGD0kxI48v8QEVVZd744Phi4) - Coder's Tape  (2019)