Ability to remove specific lines from the md output

[dadhi]

This way we can remove namespaces abd using noise from the documet if needed.

Example:

using System; // no-md

[dadhi]

Btw, it can be done with the help of collapsible section like this:

using (...)

using System;
using System.IO;
using CsToMd;
using static System.Console;

[dadhi]

added support for the default cstomd.config or for the config file provided as a second argument in the Dotnet CLI tool.

[dadhi]

Btw, it can be done with the help of collapsible section like this:

It is covered by #6