Add release notes for ML.NET 0.5

[GalOshri]

This adds release notes for ML.NET 0.5.

[CESARDELATORRE]

The notes say "This transform uses TensorFlowSharp". However, we're not really taking a dependency on TFSharp such as using its library or NuGet package, but we're taking the OSS code from TFSharp.
My point is that if we're not taking a dependency to a real library/NuGet package we shouldn't say it in that way, right?
Maybe something like:
The internal code implementation for scoring a TensorFlow model is based on TensorFlowSharp.

[GalOshri]

Good catch @CESARDELATORRE. I've updated the notes.

[CESARDELATORRE]

Looks good to me! 👍