[transducer-stats] Adding Kalman filter

[NoFishLikeIan]

I am currently working on a Kalman Filter using umbrella for a personal project. If it is of interest, I can make some tweaks and add tests, and then submit a PR to add it as a function in transducers-stats package.

[postspectacular]

Hey @NoFishLikeIan - thank you - this would indeed be a great/useful addition!