Add Catalan README (#399)

* README.md: Catalan translation draft.

* Improvements to the Catalan translation. Thanks for reviewing @oriolarcas

* Add Catalan version to German README

* Add Catalan version to Spanish README

* Add Catalan version to Indonesian README

* Add Catalan version to Hindi README

* Add Catalan version to Indonesian README

* Add Catalan version to Italian README

* Add Catalan version to Korean README

* Add Catalan version to Portuguese README

* Add Catalan version to Russian README

* Add Catalan version to Simplified Chinese README

* Add Catalan version to Traditional Chinese README

README.md

@@ -3,6 +3,7 @@
 
 :crossed_flags:
 [Bahasa Indonesia][ID],
+[Català][CA],
 [Deutsch][DE],
 **English**,
 [Español][ES],
@@ -17,6 +18,7 @@
 
 
 [ID]:README.id.md
+[CA]:README.ca.md
 [DE]:README.de.md
 [EN]:README.md
 [ES]:README.es.md