Add PSD marginalised GWT likelihoods
If there is interest, I would like to add the likelihoods which marginalise over the uncertainty in averaged PSDs to the codebase. See https://arxiv.org/abs/2006.05292 for details and https://github.com/ColmTalbot/median-marginalised-distributions/blob/master/src/likelihood.py.
I know @gregory.ashton and @avi.vajpeyi have worked with similar likelihoods in the past.