Nu upgraded to SDL3!

This release is primarily about @Happypig375's update of SDL2 to SDL3!

Additionally, we've added opt-in support for ASTC compression via KTX images for our upcoming support of Mac, iOS, and Android via the vulkan branch.

The other perhaps interesting thing is that we've now got Devin tweaked just enough to make its auto-generated wiki potentially useful in practice, which you can find here -

Changed in Detail -

• BREAKING CHANGE: Removed SDL2-CS from projects. You will need to remove this from your user fsproj as well!
• Merge pull request #1323 [from Happypig375/patch-58]
• No longer serializing EditWhileAdvancing in Gaia to reduce confusion.
• Fixed ImGui name conflict.
• Merged sdl3.
• Removed no longer necessary SDL install scripting.
• Removed no longer useful solution build scripts.
• Added support for ASTC compression format via KTX.
• Fixed explicit property appending for other simulants.
• Updated Prime with fix for #1335.
• BREAKING CHANGE: Renamed lens (<--) operator to (<~).
• Added Devin wiki generation Nu-specific instructions.

Full Changelog: v19.15.0...v19.16.0