Change NameId to be public and add method in FontDescription to be able to access the private NameTable

[JimBobSquarePants]

Discussed in #206

^{Originally posted by beeradmoore September 11, 2021}
Recently I was having an issue of getting the font name in the format I expecting to find. I found that the type of name is called a postscript name. Looking through the source I found the enum which would allow me to access it in NameIds.

Looking into how FontDescription interacts with a NameId (for an existing call that does work) I can see that it calls FontName which then calls FontName on the private NameTable which would then call GetNameById.

For my quick fix to get an app out for testing on a Friday afternoon I just added my own PostscriptName method which follows the same pattern as above.

I propose that NameId enum should not be internal, and FontDescription should have a GetNameById so that the user can get any property that is already loaded into the NameTable.

This was first mentioned in discussion #155.