feat: add `plot_recipe()` method to `FitRecipe`

[cadenmyers13]

Problem

It would be nice to have a tool so users can run recipe.plot_recipe() and it plots the fit/data.

Proposed solution

There are two cases I can think of where a user would use this,

1. Before the recipe is refined to see if initial guesses are good or just to look at the data
2. After refinement to see how the fit performed.

Add this method to FitRecipe. It should have the option to plot only the data, only the fit, or only the difference curve but the default is all three. Make it have default parameters like label names, difference curve offset, etc that people can change. This would be useful to quickly plot data and also develop paper-ready figures.