This is the minimum* amount of code required to add a new race to Rimworld. Feel free to fork and extend to your hearts content!
It depends on the Humanoid Alien Races mod. Follow the guide over at their Wiki to learn how to customise this race further.
We include the excellent Beautiful Bodies textures by ireth92. Use these as a starting point for your own races. It's worth noting that the outline of each texture matches the vanilla Humans in game, to ensure that clothes and other apparel fit perfectly. It's recommended that you do the same.
*To make this code minimal, but flexible, we copy the base Human traits. We beleive this gives any future modders more flexibility. You can leave these values alone and keep your race Humanlike, or modify everything as much as you want!