JOSS doc changes

[AnthonyLim23]

As part of the JOSS review I will need to rewrite some of the docs. The plan is to have the following:

Introduction

• what is bayes? - priors, models, posteriors
• why use bayes? - to get the probability of a model and why this is important
• Discussion on comparison to other methods (AIC, BIC and nested sampling and MCMC)

Theory

• executive summary of the main equation and assumptions
• derive the main equation and highlight the assumptions

Examples

• QENS data to identify the number of peaks present
• Identifying the number of decays in muon spectroscopy data
• Background identification (with creating a new workflow)