🐛 Spellcheck comments (#22496)

codespell -q 3 --builtin=clear,rare,informal,code -S ./Marlin/src/lcd/language -L alo,amin,endcode,stdio,uint

Marlin/src/core/macros.h

@@ -399,7 +399,7 @@
     template <typename T, typename ... Args> struct first_type_of { typedef T type; };
     template <typename T> struct first_type_of<T> { typedef T type; };
   }
-  // C++11 solution using SFINAE to detect the existance of a member in a class at compile time.
+  // C++11 solution using SFINAE to detect the existence of a member in a class at compile time.
   // It creates a HasMember<Type> structure containing 'value' set to true if the member exists
   #define HAS_MEMBER_IMPL(Member) \
     namespace Private { \

Marlin/src/core/serial_hook.h

@@ -109,7 +109,7 @@ struct ConditionalSerial : public SerialBase< ConditionalSerial<SerialT> > {
   ConditionalSerial(bool & conditionVariable, SerialT & out, const bool e) : BaseClassT(e), condition(conditionVariable), out(out) {}
 };
 
-// A simple foward class that taking a reference to an existing serial instance (likely created in their respective framework)
+// A simple forward class that taking a reference to an existing serial instance (likely created in their respective framework)
 template <class SerialT>
 struct ForwardSerial : public SerialBase< ForwardSerial<SerialT> > {
   typedef SerialBase< ForwardSerial<SerialT> > BaseClassT;