For a writer today working in the professional world, the three big skill sets sought now are in Web Development, Graphic Design and Post Production. At least the basics. This is so an employer can have faith that you can be self-sufficient whether it’s creating a print ad or short ad/video or even posting to/creating web sites.
In today’s market, especially with the rise of freelance, employers expect a writer that can be almost-entrepreneurial in their work. Which already should be the mindset of any writer anyway. Since you are in the business of you as a writer, wouldn’t you want to be able to offer the best product possible?