Replace the library ExcelNumberFormat for our own implementation

[rliberoff]

Currently, the Excel connector that reads Excel files and transforms them into Markdown for AI LLMs uses a library called ExcelNumberFormat. It is available here: https://github.com/andersnm/ExcelNumberFormat

The issue is this library is rather old (no new updates since 2020) and belongs to a source that is not really know. The code of this library is quite simple, so we should be able to create an improved and modernized copy (using the latest features of C# language) and take control of the implementation. Obviously, we should mention the original author in the corresponding README.md.

I think the best place to code this is in Encamina.Enmarcha.Core. I would not bind the name of the code to Excel, and instead name it based on the ECMA-376 standard 👉🏻 https://ecma-international.org/publications-and-standards/standards/ecma-376/