Updating existing excel blows up the size of the excel

[akashkhan25]

Thanks a lot for the library! It's been very useful 😄

I've noticed that using the writer to update existing excel will increase the excel size by over 10X even if there's very small amount of changes made.

Steps to reproduce:

1. Create an empty excel (Note the size. For me empty excel is ~ 49KB)

2. Execute the following to add some columns to the excel and write it

   let headers = vec!["column_a","column_b"];
   let mut book = umya_spreadsheet::reader::xlsx::read(path).unwrap();
   let worksheet = book.get_sheet_by_name_mut("Sheet 1").unwrap();
   let col_count = worksheet.get_highest_column() + 1;
   worksheet.insert_new_column_by_index(&col_count, &(headers.len() as u32));
   
   for (i, header_val) in headers.iter().enumerate() {
       let col_index = col_count + (i as u32);
       let cell = worksheet.get_cell_by_column_and_row_mut(&col_index, 2);
       cell.set_value(header_val);
   }
   umya_spreadsheet::writer::xlsx::write(&book, path)

3. The size of the excel is now 630KB.

Note: Opening the file in Excel and saving without any changes will fix the file size back to expected size.

Originally I noticed it on adding even 1 column on an input of size 500KB blew up the file size to 5.6MB. Reading it back caused memory usage to spike

[akashkhan25]

After debugging a bit, it seems to be due to using Stored compression method . Applying the change from #106 seems to resolve the issue . So if that PR is okay to merge I'll close this 🙇

[MathNya]

Thank you for your report. I have merged #106. We will release it as ver 0.9.1 soon.