FftSharp 2.2.0

• Added support for .NET 8 (#83) @msft-takend
• FftSharp.Bluestein now has Forward() and Inverse() methods for calculating DFT using Bluestein's chirp z-transform algorithm for arrays of any length (#77) @gsgou
• FftSharp.DFT has Forward() and Inverse() methods for calculating DFT (simply but inefficiently) moved out of the Experimental class
• Updated tests, documentation, and demo application to use ScottPlot 5 (https://ScottPlot.net)
• Removed FftSharp.Complex and related methods which have been marked Obsolete for over a year. All methods now use System.Numerics.Complex