Add Kashubian to languages dropdown (#26024)

app/helpers/languages_helper.rb

@@ -191,6 +191,7 @@ module LanguagesHelper
     chr: ['Cherokee', 'ᏣᎳᎩ ᎦᏬᏂᎯᏍᏗ'].freeze,
     ckb: ['Sorani (Kurdish)', 'سۆرانی'].freeze,
     cnr: ['Montenegrin', 'crnogorski'].freeze,
+    csb: ['Kashubian', 'Kaszëbsczi'].freeze,
     jbo: ['Lojban', 'la .lojban.'].freeze,
     kab: ['Kabyle', 'Taqbaylit'].freeze,
     ldn: ['Láadan', 'Láadan'].freeze,