[RFC] Using a major version bump for syntax opt-in

Hello everyone, I wanted to gather some opinions on whether my thinking in Let recipes read attributes without hard-coding canonical names - Pull Request #5786 - JuliaPlots/Plots.jl - GitHub is a good thing to do or not. So the issue is that in Plots recipes users didn’t have a way to get the value of some plotattribute in way that does not leak internal API, namely the internal name of a plotattribute. The PR should provide dedicated syntax for that. That in itself is a new feature and does ...