AK: Add Utf16View::to_utf8 to convert the view to a UTF-8 AK::String

Author: https://github.com/trflynn89
Commit: 2eacc7aec1
Pull-request: https://github.com/SerenityOS/serenity/pull/16926

AK/Utf16View.h

@@ -12,6 +12,7 @@
 #include <AK/Forward.h>
 #include <AK/Optional.h>
 #include <AK/Span.h>
+#include <AK/String.h>
 #include <AK/Types.h>
 #include <AK/Vector.h>
 
@@ -76,6 +77,7 @@ public:
     };
 
     ErrorOr<DeprecatedString> to_deprecated_string(AllowInvalidCodeUnits = AllowInvalidCodeUnits::No) const;
+    ErrorOr<String> to_utf8(AllowInvalidCodeUnits = AllowInvalidCodeUnits::No) const;
 
     bool is_null() const { return m_code_units.is_null(); }
     bool is_empty() const { return m_code_units.is_empty(); }