Version 2.10

Here's the full list of changes:

- Updated to the latest 2021 version of Unity.
- Updated to the latest version of Steamworks.NET.
- Updated to the latest XCode and iOS build target.

I update the tools and development environment about once per year. I rarely use the latest software because there's often issues with updates and I don't like to waste time to constantly learn new stuff when I can waste a lot of time in one go.

This time was no different and now after a few days I finally got a version out that seems to work like it did while using older tools.

So, I updated the tools from 2020 to 2021 and only one version of the three (Win, Tux, Mac) worked straight out of the box while the two others simply crashed on startup.

After some ducking around the net I finally figured out what might be the reason why those other two didn't work and then it was just trial and error while tweaking the settings.

It's always fun when new default options do not work unless some hidden option is selected correctly. It's even more fun when there's no indication that they don't work until you have uploaded the new build and test it in release environment and then it says derp.

Anyway, there's nothing new content-wise but hopefully this little exercise in frustration makes future updates smoother.