Support Custom Domain Configuration via CNAME file

[fingers10]

Hi @jsakamoto ,

It will be great if this package supports a way to add configuration to enable custom domain via CNAME file while publishing.

For Example,
In .csproj,
<CNAME>ilovedotnet.org</CNAME>

When CNAME property is given it should override GHPagesBase as <GHPagesBase>/</GHPagesBase> and generate CNAME file in the publish output with domain name as its content.

CNAME file in Publish Output:

Content of CNAME file:

This will help to setup custom domain easily.

Please can you share your inputs on this?

Thanks,
@fingers10