Improve library with nullable reference types

Nullable reference types (NRTs) were introduced in C# 8 to help developers understand their usage of null values throughout their code to avoid unexpected exceptions on edge cases or explicitly mark values as nullable if they are intended to be. More information can be found in the official Microsoft docs.

I feel like security critical libraries like this one could really benefit from implementing this feature for the following reasons:

1. It would improve the library code itself by ensuring all possible null cases are accounted for (Ex: Adding null checks or making variables nullable).
   • This is important because even if the current code is null safe without this feature now, future code may introduce edge cases that aren’t caught. This feature could help prevent that from happening.
2. Consumers of the library who also have the feature enabled will get the nullable signatures from this library to keep their code safer as well.
   • More info: Microsoft dev blog

I would be very happy to attempt integrating this feature into the code if you support the idea.

[AndrewTriesToCode]

🎉 This issue has been resolved in version 6.6.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[fossbrandon]

Yup! Thanks for reopening and sorry for the delay on this last one. I’m mostly done with it but life got pretty busy. I should have a PR within the next week though.