[Docs] Add README.md to FsSpreadsheet.Interactive

[Freymaurer]

README should contain minor information about scope of project

[HLWeil]

@kMutagene, I don't even know what this project does. Is it still relevant?

[kMutagene]

Display of sheet object as table in notebooks

[HLWeil]

Works like a charm btw! Just tested it!

[HLWeil]

#107