Incorrect information in "For Modders" section of README.md

[sandsalamand]

The "For Modders" section of README.md, https://github.com/amazingalek/owml#for-modders, states:

"1. Create a C# class library project targeting .Net Framework 4.0."

However, the Nuget package states that OWML is only compatible with .Net Framework 4.8