Some C# keywords are not highlighted

[ghost]

I know I can submit a PR. But doing so will trigger a CI build and will waste CI time. I will update C# keywords that are currently not in the language file here for you to add.

Currently, I only found #elif, #endif, nint, and nuint.

BTW, it seems #if is not correctly recognized. # character is not highlighted. It seems ecode thinks #if is the if statement.

[SpartanJ]

Thanks, i'll add them later.

[SpartanJ]

Added.