feat: spellcheck input (#6446)

Reviewed-by: Mm2PL <mm2pl+gh@kotmisia.pl>
Reviewed-by: pajlada <rasmus.karlsson@pajlada.com>
Reviewed-by: fourtf <tf.four@gmail.com>

src/singletons/Settings.hpp

@@ -353,6 +353,9 @@ public:
         false,
     };
 
+    BoolSetting enableSpellChecking = {"/behaviour/spellChecking/enabled",
+                                       false};
+
     FloatSetting pauseOnHoverDuration = {"/behaviour/pauseOnHoverDuration", 0};
     EnumSetting<Qt::KeyboardModifier> pauseChatModifier = {
         "/behaviour/pauseChatModifier", Qt::KeyboardModifier::NoModifier};