Update documentation for primitives based function

[woodsp-ibm]

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What is the expected enhancement?

Some of this, in regards of API ref will come naturally from the inclusion of the new function. Other aspects require more direct action e.g.

• [ ] Update ML overview in API ref in docs\index.rst
• [ ] Update readme (which seems to be reflect the above text); also update its sample code
• [ ] Migration guide covering transition from old to new function

[woodsp-ibm]

Maybe also can check over docs and adjust class one-liners to improve the auto generated tables e.g. this is what kernels looks like at present which seems like it could be improved