Upgrade the project to .net 8.0 and fix high security vulnerabilities (one failing test remaining)

[DamirTomic]

Hi, I wanted to fix a dependency that is rated a high-security vulnerability, but in order to do that I had to make significant upgrades to the project, such as upgrading it to .net 8.0. I hope you're ok with that, if not, we can discuss.

There is 1 test that's failing but I think the test is incorrectly written. I can fix it we agree on a solution
a) test shouldn't throw an exception if you pass a valid string but the file doesn't exist
b) test should throw a filenotfound exception or something like that if the string exists but the file path doesn't
c) other ?

[toddams]

Hey Damir

Thans for your PR, it's very valuable missing piece we had. However, because you replaced tabs with spaces on certain files (but not all of them, though) - it completely messed up the diff, and it's hard to tell what was changed without going line by line.

Also, dropping netstandard is going to make library unusable for some people, which I'd like to avoid. Are you sure there is no way to have updated packages without vulnerabilities without dropping it?

I also noticed, that #if directives for runtime-specific areas were not changed

[DamirTomic]

Ok, let me see if I can make this work with .net standard, and I'll fix the other things as well.