qax-os/excelize ? reverse-engineered prompt

Build me a pure Go library for working with Excel files, mainly XLSX, XLSM, XLAM, XLTM, and XLTX. I want to be able to create new spreadsheets, open existing ones, read and write cell values, get rows back, and save the file again. It should also handle the more practical Excel stuff people actually use, like styles, merged cells, tables, charts, pictures, data validation, pivot tables, slicers, sparklines, shapes, and streaming support for big worksheets so it does not use too much memory.

Please make the library easy to use with simple methods for common tasks, and make sure it can work with Excel files made by modern Microsoft Excel. Include good examples in the README for creating a workbook, reading data, adding a chart, and inserting an image. Add tests for the main features and keep the code clean and well organized. If you need to check anything, look up the current docs online first.