c#: Add new channel type entry (attention)

[dNechita]

PR Description

Keep the channel types from the C# bindings in sync with the ones within the libiio library.

PR Type

• Bug fix (a change that fixes an issue)
• New feature (a change that adds new functionality)
• Breaking change (a change that affects other repos or cause CIs to fail)

PR Checklist

• I have conducted a self-review of my own code changes
• I have commented new code, particulary complex or unclear areas
• I have checked that I did not intoduced new warnings or errors (CI output)
• I have checked that components that use libiio did not get broken
• I have updated the documentation accordingly (GitHub Pages, READMEs, etc)

[rgetz]

You may want to update ./CI/azure/check_kernel.sh to check bindings/csharp/Channel.cs and bindings/python/iio.py so we don't forget to this in the future. Nothing like getting a reminder to fix something. :)

[dNechita]

You may want to update ./CI/azure/check_kernel.sh to check bindings/csharp/Channel.cs and bindings/python/iio.py so we don't forget to this in the future. Nothing like getting a reminder to fix something. :)

A true pleasure indeed :)
I have put up checks for both C# and Python that should enforce keeping everything in sync. Thanks for suggesting it!