v0.0.6

[thomaspinder]

Incremenet JaxKern to v0.0.6.

• Alter backend to work with new Parameters object from JaxUtils
• Implement Random Fourier Features
• Clean up the __init__ method of the AbstractKernel
• Implement the StationaryKernel abstraction

Resolves issues: JaxGaussianProcesses/GPJax#213, JaxGaussianProcesses/GPJax#214, JaxGaussianProcesses/JaxKern#52, JaxGaussianProcesses/GPJax#215, JaxGaussianProcesses/GPJax#216, JaxGaussianProcesses/JaxKern#39, JaxGaussianProcesses/JaxKern#30