Allow skipping encoding command in output

[Ovid]

Hi there,

In OpenAPI, it's common to use Markdown inside. However, I'm writing Perl code from OpenAPI documents and the POD is not an entire document, but a partial document because I am grabbing descriptions from various sections of the OpenAPI routes and building them into a class. That leaves me with the following code:

                    $description = $markdown->markdown_to_pod(
                        encoding => 'utf8',
                        markdown => $resolved->{description},
                    );

                    # Markdown::Pod adds this, but we don't want it because
                    # we're creating snippets of POD, not the entire document
                    $description =~ s/\A=encoding utf8\n\n//;
                    $resolved->{description} = $description;

It would be nice if I could just do this:

                    $description = $markdown->markdown_to_pod(
                        encoding => 'utf8',
                        markdown => $resolved->{description},
                        fragment  => 1, # needs much better name!
                    );

And not get the =encoding utf8 added.