Merge branch 'fs-mem-string-data'

Use UTF-8 for memory FS data if it's not in Latin-1.

See https://github.com/wxWidgets/wxWidgets/pull/2622

See #19314.

interface/wx/fs_mem.h

@@ -83,6 +83,12 @@ public:
         Stored data (bitmap, text or raw data) will be copied into private memory
         stream and available under name @c "memory:" + @e filename.
 
+        When using the overload taking @c wxString data, if the string contains
+        only Latin-1 characters (which includes strings created using
+        wxString::From8BitData()), its data is used as is. Otherwise, the UTF-8
+        representation of the string is stored as the data associated with the
+        given @a filename.
+
         @note you must use a @a type value (aka image format) that wxWidgets
               can save (e.g. JPG, PNG, see wxImage documentation)!