v0.12.0

This release contains several major new features:

• Greatly improved functionality for estimating treatment effects with instrumental variables (#460)
• A variant of DoubleML for use on dynamic data (#446)
• A new class for assessing the causal contributions of different features to an outcome, conditional on the other features (this is spread out over a number of PRs)

There have been a few breaking changes:

• Alpha values for confidence intervals now always default to 0.05; previously some alphas defaulted to 0.1 instead (#482)
• The deprecated ability to pass X, W, and Z to some fit and score methods by position has been removed (#482)

There have also been many bug fixes in this release; we'd particularly like to highlight:

• Default values of alpha are now passed correctly through results classes (#476, thanks @mtanghu!)
• Prevent NaN outputs from GRF in certain corner cases (#480, thanks @arose13!)