Add support for Tabs

[PrzemyslawKlys]

This PR solves:

• https://github.com/EvotecIT/OfficeIMO/issues/126

Add ability to add tabs to the document.

public static void Example_BasicWordWithTabs(string folderPath, bool openWord) {
    Console.WriteLine("[*] Creating standard document with tabs");
    string filePath = System.IO.Path.Combine(folderPath, "BasicWordWithTabs.docx");
    using (WordDocument document = WordDocument.Create(filePath)) {
        var paragraph1 = document.AddParagraph("To jest po polsku").AddTab().AddTab().AddText("Test");

        Console.WriteLine(document.Paragraphs.Count);

        Console.WriteLine(document.Paragraphs[1].IsTabChar);
        Console.WriteLine(document.Paragraphs[2].IsTabChar);

        Console.WriteLine(paragraph1.IsTabChar);

        var paragraph2 = document.AddParagraph("Adding paragraph1 with some text and pressing ENTER").AddTab();

        Console.WriteLine(document.Paragraphs.Count);

        Console.WriteLine(paragraph2.IsTabChar);

        paragraph2.TabChar.Remove();
        document.Save(openWord);
    }
}