Learn how to share your ideas and opinions in a concise, engaging way. Learn to advocate for (or against) something in a way that will have people engaged (first point: never be combative, people will mostly dismiss you as immature or emotionally compromised).
Yeah it doesn't sound like a "tech skill" but it absolutely is and I think too many "tech" people severely undervalue it, preferring instead pure "lone wolf" kind of skills that don't require the squishy, dirty aspects of dealing with other humans (speaking from personal experience here).
You can accomplish a lot on your own with the right talent and skills. But you can always accomplish more if you can engage more people.
Maintain a blog of interesting things you've learned, hiring managers will value the demonstrated writing skills.