Need to add other writes methods ;

• Override of actual write method (with x and y args)
• Add write methods which precise the type of data to put in the file (string, number, formula (maybe not now), url) (formulas, url etc... will be added later)

When reading .xlsx, e.g. with d1ceward/xlsx-parser, nil cells can be valid results.

However, when writing with this library, this is not possible, see e.g.

def write_row(pos_y : Int32 | Int64, data : Array(Int32 | Int64 | Float64 | String))

Be able to apply style to cells, texts and tables

Implement the feature to add tables in the excel document.
Excepted features are :

• Table with or without header
• Enable or disable autofilter
• First and last column highlight
• Add a title to it
• Total row feature
• Finally : choose properties for each column

Tables' styles will come with another feature I think