Add fw dumping

- also fatfs is stupid
- also close files properly on a failed copy
- also check for errors during folder readouts
- also make sure holding vol- doesn't dump the keys anyway

source/fs/fsutils.c

@@ -42,4 +42,13 @@ char *GetFileAttribs(FSEntry_t entry){
     char *ret = CpyStr("RHSVDA");
     MaskIn(ret, entry.optionUnion, '-');
     return ret;
-}
+}
+
+bool FileExists(char* path){
+    FRESULT fr;
+    FILINFO fno;
+
+    fr = f_stat(path, &fno);
+
+    return !(fr & FR_NO_FILE);
+}