clarified why .data is listed as both ROM and RAM in the FAQ

Author: BartMassey

faq.md

@@ -245,7 +245,8 @@ Total               555960
 Of the standard sections, `.vector_table`, `.text`, `.rodata` and `.data` will
 occupy Flash / ROM; `.bss` and `.data` will occupy RAM; `.debug_*`,
 `.ARM.attributes` and `.comments` can be ignored as they won't be loaded into
-the target device memory. For the other sections you'll have to check your
+the target device memory. (`.data` is initially placed in
+Flash / ROM, but copied to RAM during startup to make it writable.) For the other sections you'll have to check your
 dependencies' docs.
 
 In this example the uploaded software will occupy `2008` bytes of Flash.