Unity3D's 2020.2 release is now supporting C# 8 and nullable reference types. The default way to opt in to this language feature is to put <Nullable>enable</Nullable> in your .csproj file, but Unity regenerates .csproj and removes this line every time it compiles.
Is there a way to insert custom content into my .csproj, or do I need to fall back to the tedious process of starting every file with #nullable enable?